[longhornchris04]

If its a CA car and still has / had all the emissions stuff, then is the engine in good shape?

I have a '75 w/ an SC motor but I did a bunch of research (including the forums here) and found that the '75s, especially the CA cars tend to have major reliability issues with valve guide wear. If those have already been rebuilt by a PO then you are fine. If not, the you are probably looking at a rebuild anyway, which

1 - costs money... perhaps more than you want if you were going to put a 3.0/3.2 from a donor vehicle in later (bad side)

2 - reduces the opportunity cost for the best HP mods. After all, even if it is just a top-end rebuild, you can put in new cams and other stuff. (good side)

As for bolt-ons, I'd second (third perhaps) the SSIs & and good sport muffler. If you aren't going to change the CIS (expensive) then a "performance" air filter won't do squat.

A bit off-topic, but if you are planning on replacing the engine, consider mods you can take to the next engine. Obviously anything non-engine (suspension, brakes, etc), as well as engine stuff that could go on the next engine. If you go with a CIS-SC motor then there should be a decent number of things that will transfer.