My doomed 408 build

I was running out of cam that's why I was maxing power out at 5000 RPM.

Or...... you were running out of valve spring.

408 with 63cc heads, zero deck, 5cc pistons, .040 gasket.......about 11.6cr.

In any case, I hope it works out to your satisfaction.
When I was first getting into it many years ago, I did it the way I wanted.
Sometimes it worked out really well, sometimes not so much.
But that’s how you learn.