J (915) vs. Magnum heads
Depending on your eventual goals, RHS and edelbrock heads are available in magnum configuration.
There's also EQ heads which are a very impressive unit.
fwiw, I run J heads on my engine and I truly love them. BUT I bought them when I was 18 for $500 AUD and got new guides fitted and a performance valve job done on them, I have recently had the bowls ported for more performance.
They're good heads, but if I had known then what I know now I would have paid a little more, been a little more patient and started with something better.
That's why I have a set of edelbrocks sitting on a shelf, still in their boxes waiting for my next engine build.
Hmm actually maybe patience still isn't really my thing after all.:D