What was in your car before. A 318 or 360 will go in perfectly as with a 4 speed. Did your car have a slant six, was it manual or automatic transmission. Give us details of what you have then you’ll get more answers than you can handle.
It originally had slant 6 3 speed trans not sure of rear but I imagine it is small I would like a large V8 with @least 350 horse 4 speed trans and street strip rear and 15inch tires @least in back