A couple of A-body rookie questions.

Redneck,

As an early A-body owner for 20+ years I can say this.....
You can yo-yo engines and transmissions all day, but once you cut the car up, its just another cut up car. If the body is in perfect condition I would leave it as it is, a 360 is ok, a well tuned 904 is pretty good too.

A body with lots of rust to me is easier justified to put in a 4spd only because it will never be a perfect "untouched" car. If you are going to go the route of 4spds and total resto go all the way a commando 4spd formula s gold on gold car is one of the rarest.....