I have two sets of good known heads, J heads and a set of 318 heads. I have a gasket kit. I will probably have the bores measured just to set my mind at ease on the piston and rings.
Well, which heads are they? Js or 308s?
308s were original 360 roller heads, they do not require any pushrod hole clearancing at all. Js, however, were HFT heads and do need the holes clearanced.
The 318 heads you referred to, I assume are the original heads from your 318 roller motor; which would be 302s. Obviously, no mods needed there for them to work, they already have hardened seats, and a smaller combustion chamber than either the Js or the 308s that will keep your compression ratio where it belongs on a stock 318 roller.