Thanks @Mattax for posting that. Such a simple and honest question has so many rules explaining stuff.
Dan, I wouldn’t touch 302 heads if you paid me to run them. If you produce a 6 figure envelope, don’t expect me to campaign a season!
IF you want to increase the performance of any engine, but we will focus on the 318 for the moment specifically, I’ll tell you what I would do and that would be a set of Edelbrock heads. I’m not a big Speedmaster fan. BUT! If the work ($$$$$$) for you, go right ahead.
Screw J heads, to much work for a smaller payout than an aluminum head.