Does the body of the car matter if I want to put an aftermarket engine in?

It matters if the car is built to take a V8. A V6 car may be FWD or not have room for a bigger engine.

Also, if you're asking about a Firebird or Camaro it matters a great deal! There's a laundry list of things that need to be changed or modified for a V8 to go into a V6 Firebird or Camaro. Everything from the motor mounts to the suspension to the accelerator cable needs to be changed or modified to accommodate the V8. Not worth it in my opinion! Hope that helps! Jim

Tell us what car you have in mind if you want more advice.