Installing 302 heads is exactly what I did on the 318 in the Demon. Coupled with the 68 pistons, I have a little bit of a sleeper on my hands. The 302 heads came out in 85 and were used through the end of LA 318 production in 91. All you want will be the head assemblies. Check for cracks, no burned valves, clean up, new seals, and run 'em til you're tired of 'em.
I used flat hydraulic tappets on my build up and stock pushrods. No changes were needed to the rocker gear. My heads came off an 86 Diplomat in a Pik-n-Pull lot. All I did was what I suggested. Since I am running a stouter than stock cam, I did change the springs. Even with the spring change, I am out less than $150.