Intro

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.

Motor

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.

Transmission

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:

If you're using a manual transmission, the story is much simpler; just find a small-block bellhousing for your transmission.

1963-1964

'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.

1965

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.

1966

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.

Steering Linkage

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.

Throttle Linkage

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

Exhaust Manifolds

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 that yet.

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.

Motor Mounts

The original motor mounts are yet another '64-'66 A-body V8 car only part. Luckily, Schumacher Creative Services does make a part 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 well anyway.

Radiator

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 brackets.

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.

Other Considerations

There are a few other things to keep in mind when doing this swap.