302 heads are a bolt on as with 308s,the 308 have 1.88/1.60 valves and both will improve compression. I had a set of 302s opened up for 1.88/1.60 valves,did some porting and put them on with a set of .022 gaskets on a 88 318 along with other goodies. I can tell you it is surprising the differences there is. Unless you go with an aftermarket aluminum set that is probably the easiest choice.
