318 heads on a 360?
Yes, you can install the 318 heads on a 360. There really is no benefit though. IMHO home ported and polished 318 heads on a 360 will only "restrict" rpm like BJR pointed out., because the port volume is less.
I have a really nice set of swirl port 308' casting 360 heads in the classifieds...shoot me an offer on them.
They are swirl port, 72cc, and designed with a 360 in mind.