will J heads work on a 318? And many many more questions.

+1. they will work just fine, a slight loss of bottom end is well worth the gain of top end. IMO. note the comp ratio will most likely drop slightly due to the larger 72cc chamber volume. only the 273 has interference problems with intake valve and cyl. wall. 2.02" and 1.88" valve will clear without trouble on a 318. good luck.