The A-Body platform was originally designed to use the then-new slant-6
engine. However, midway through the 1964 model year, the new LA engine
was offered at 273 cubic inches. Swapping in a small-block V8 is certainly
possible, if you can find all the right parts. Additionally, each year has
its own little issues.
The first thing you'll need is a motor. Any LA small block will do
(273, 318, 340, 360), since they have the same
external dimentions. Motors that
will not work, without major structual changes, are the older poly-head 318s,
big blocks (361-440) and Hemis.
Make sure you get all the brackets for your accessories like power steering
pump and alternator, since the slant-6 pieces are not the same.
A lot of transmission changes were happening at Chrysler during this time
period. All of the early A-Body factory V8s used some form of the 904 auto
or the 833 4-speed. You'll have to find a transmission that matches up
with the rest of your car.
There are two main auto transmissions used by Mopar in this time period:
904 and 727. They are functionally the same, although the 727 case is
physically larger. In addition, depending on what motor the transmission
was used with, it had a different bellhousing. To make things more
confusing, '65 and earlier transmissions were operated with two cables,
while '66 and later used a single rod linkage. And finally, the connection
from the transmission to the driveshaft changed from ball-and-trunion
to slip-yoke in '65 (for B-bodies) and '66 (for A-bodies).
And I'm not even getting to the earlier cast-iron cases, and the later input
shaft spline changes...
That leaves us with 9 different transmissions during this time period:
- slant-6 904 cable shift ball-and-trunion (60-65)
- slant-6 904 rod shift slip-yoke ('66-up)
- small-block 904 cable shift ball-and-trunion ('64-'65)
- small-block 904 rod shift slip-yoke ('66-up)
- small-block 727 cable shift ball-and-trunion (early-'64 B-body 318s)
- small-block 727 cable shift slip-yoke ('65 only B-body 318s)
- big block 727 cable shift ball-and-trunion (early-'64)
- big-block 727 cable shift slip-yoke ('65 only)
- big-block 727 rod shift slip-yoke ('66-up)
If you're using a manual transmission, the story is much simpler; just
small-block bellhousing for your transmission.
'63 and '64 used a pushbutton mechanism in the dash to select gears. The
'64 small-block 904 is a direct swap-in for these cars. The '65 small-block
904 will work, but may require you to use a '63 or '64 valve body.
In 1965, NHTSA rule changes outlawed the pushbuttons. Most cars used a
steering column mounted lever, but the Dart GTs and Valiant Signets could
be had with a floor mounted shifter. Even though the gears were selected
with a lever, they still used two cables to work the transmission. The
transmission cases for '65 are the same as '64, but the valve bodies may
not be. Also, the valve body may be different between the column shifted
cars and the floor shifted cars. If anyone has better information on this,
please let me know.
For 1966, Mopar redesigned their transmissions to use a single rod to
change gears, which made the whole linkage much simpler. You can use any
'66 and up small-block 904, providing you use a torque convertor with the
same number of splines as the input shaft of the transmission.
Transmission swaps requiring more work
You can use an aftermarket floor shifter mechanism on a '65 and earlier car
to allow you to use a rod-shifted transmission. To make things look nicer,
you'll want to find a steering column without a shift lever (any '63-'65
except the '65 column-mounted shifter one). And for the '63 and '64, the
trim piece used to cover up where the pushbuttons go used which was used
on manual transmission cars.
A 727 may also work, if you do some modification of the transmission tunnel
with a large hammer. Cable shift small block 727s were used in B-bodies with
poly 318s in 1965 and earlier. Rod shifted small block 727s were used in
later 340 powered cars, some 360 cars, and some taxi and cop-spec cars.
The suspension centrelink (the piece that goes between the pitman arm and
idler arm) was different between the V8 and slant-6 cars. Since the oil
pan on the V8 sits closer to the ground than on a slant-6, the the centrelink
on a V8 car drops down to clear the pan.
This is a '64-'66 A-body V8 car
only piece, and no one makes reproductions. If you are unable to find the
right part, your only option is to alter your V8 oil pan, either by denting
it up, or cutting a piece out and welding it up to clear the suspension.
Most, if not all, early A-bodies with slant-6's used a rigid rod that
rotates as a throttle linkage. All V8, as well as later slant-6 cars, used
a flexible cable instead. There's no straightforward way to adapt the
rigid rod to work a carburator on a V8. The sure-fire way to make it work is
to get the accelerator pedal and cable from a '64-'66 V8 A-body. The same
parts from a '67-'76 V8 A-body may also work
The original exhaust manifolds are '64-'66 A-body V8 car only items. The
passenger-side manifold is a pretty normal
looking part, but the driver's side manifold
has a distinct bend in the outlet tube that allows it to
snake down and around, between the motor and the steering box. Of course,
no one makes reproductions of these. It's rumored that later A-body 340
exhaust manifolds can be modified to work, but I can't find a reference to
For headers, here
is a link showing the only set of headers I know of that fit an early A-body
without getting out the cutting torch. Unfortunately, they currently only
work on manual steering cars. The only other choice is to get fenderwell
headers which require you to cut out parts of the inner fender.
The original motor mounts are yet another
'64-'66 A-body V8 car only part. Luckily,
Schumacher Creative Services
that does the job. They might not look exactly the same as the originals, but
as small as the engine compartment is, you won't be able to see them very
The radiator in a slant-6 car is smaller than the one in a V8 car. Since
a V8 produdes more heat than a slant-6, you'll want to get a larger radiator.
Obviously, the radiator out of a '64-'66 V8 car will be a perfect fit. A
radiator out of a later A-body might fit, but you'll need to measure the
opening in your radiator support first. Also, an F-body (Volare, Aspen)
radiator could work as well, with some minor alteration of the radiator
Oil Filter Adapter
The oil filter on a Mopar small block normally sticks straight out from
the passenger side of the block. Since the engine compartment is so narrow
on these A-bodies, an adapter is required that
rotates the filter so it points toward the rear
of the car. These pieces were used on several
different cars through the years, and Mopar Performance still sells them.
There are a few other things to keep in mind when doing this swap.
- '64-'66 cars have a dimple in the firewall right behind where the
distributor would be. On a '63, you will have to make this dimple yourself,
either with a hammer or patching in that part of the firewall from a later
car, otherwise the distributor will hit the firewall.
- Since a small block is heavier than a slant-6, you may want to upgrade
to thicker torsion bars to help hold that extra weight up.
- Standard brakes on these cars were 9-inch drums, with 10-inch drums
optional on some years, all with a single circuit brake system. With more
go-power, you should also consider
adding more stopping power.
- If you are putting in a 360, you'll need the specially weighted
flexplate, torque convertor or flywheel.
- The standard rear axle was the 7 1/4", which was the weakest rear end
used by Mopar through the 60s and 70s. If your new V8 has any guts at all,
get ready to either continuously swap in replacement 7 1/4's, or put in an
8 1/4" or 8 3/4" rear.
- Make sure the water pump you're putting on the engine points its outlet
toward the lower radiator outlet. Older cars (before '67 or '68) pointed
toward the driver's side, newer ones go toward the passenger's side.
- We'll end with a bit of good news. The same K-Frame was used between
'63-'66 in A-bodies whether the car had a slant-6 or V8.