The rear axle spring perches on the F-body (Volare/Aspen) are an inch wider than the A-body. Also, the Volare axle would have be a BBP axle. There should be a metal tag on the 72 & 77 axles specifying the ratios. In all probability, both cars have a 7¼" rear end. Count number of bolts in the rear end cover plate. A 7¼ will have 9 except for the 2.45 and 2.21 rear ends which may have 10. The Volare may have an 8¼ axle. The cover plate will be round and will have 10 bolts. FWIW: The 7¼ has 2.75" axle tubes, the 8¼ has 3" tubes. Therefore, if you go to the larger axle, you'll need to have the shock plates and clips, too.
Didn't catch what trans is in your 72. If it is a 904, suggest keeping the existing driveshaft and rear axle for now.
The 77 is going to have a ton of emissions gear on it. To make it run properly in the 72, you'll need all of it. 1977 was one of the years that Mopar used a CCEGR valve that was mounted in the radiator header tank. The emissions system on the Volare used a LOT of vacuum lines. If you disconnect one, be sure you have it marked in a way that it can reattached to the correct fitting. All vacuum lines are not the same. Some are "timed" by the carburetor, others are not.
As far as actually installing the engine in your car, it will be necessary to choose between using adapter mounts, such as Schumacher Creative Services makes; or replace the K-frame with a 67-72 A-body V-8 piece. The 73-77 V-8 K-member will also work, but there may be additional issues such as anti-roll bars that might cause delays. As is, the mounting points on a 72 /6 K-frame are incompatible with the LA V-8.
The devils in the details on this conversion:
- Need an A-body LA driver side exhaust manifold or use headers. Area around steering gear is very tight.
- Cannot use a full size oil filter on A-body unless it is remote or on a 90º adapter from an A-body LA. Other option use the "shorty" filter. Long (1 qt.) filter will hit passenger side torsion bar under some situations.
