What all has to be done to an engine when installing a higher performance camshaft?
The more radical the Cam is, the more is required to make it function properly. A mild cam can be installed using all stock parts, but to go wild with the cam requires some research in order to get the right parts. I can absolutely believe that the previous owner put a mild cam in it. For a 77 302, I would certainly consider an Edelbrock performer power package, of even a performer RPM package, since it is in basically a light pinto chassis. The RPM cam works best if you use the heads, and intake, to match. So it is quite an investment. To get really crazy with a cam requires a full engine build specifically to run with it, or you wont get the expected performance. Just a really basic answer, and I hope it helps a little