I am currently building a 302 myself for a swap, im planning on running the E303 cam available from summit, i dont think your block is a roller cam setup tho i could be wrong. so you would have to run the more expensive tiebar roller lifter to swap to a hydraulic roller cam, if wanted to run flat tapet any 302 cam will fit that motor, the only different between your block and any other 302 is well nothing, if its a windsor then you can find about anything you want for those internally, if your wanting to change things like intake like someone else said just not worth it unless you go with an intirely aftermarket intake like trickflow or somthing, and as for your heads your talking about porting them, DO YOUR RESEARCH, GT40P heads can be destroyed very easyly if your not very carefull, the intake side of those heads really dosent need help, all i did with mine was polish the combustion chambers and opened up the exhaust ports to the gaskets i will be using sense they are very restricted on the exhaust side.
Any way try summitracing for parts, or talk to a machine shop.
For the head work read up on DIYporting.com good info there
Hope thats helps you a little