Need advice from the early A-body gurus....

If the work was well done, the majority of the changes I would want are already done. My 64ragtop scoots pretty well with a '74 318. A 360, tuned right should be somewhat quicker. One problem in V-8 engines in the early A body cars is the exhaust. It can be tough to find manifolds or headers that will clear the rather narrow engine bay.