Re: 6 to 8
You'll need a 302 wiring harness (its only 4 wires I think, you could probably make one if you find a diagram). You will also need 302 motors mounts - Advanced Auto can order them for you, they are pretty cheap. You'll also need to mate your old transmission to the 302, so you'll need a new bellhousing and maybe some other stuff (what trans do you have?) You will probably also need a new throttle linkage. The springs and shocks are stiffer in the front and v8 cars had 5 lug spindles.
Good luck and if you have any other questions, just post em up.
I drive a station wagon.