Speedmaster spark plug holes improvement??

I estimate that a more well thought out overall combination of parts could have bettered that 331hp by another 40-50hp without really spending any more $$$.
Mainly, compression and the intake manifold.

The XE268 in a small block with half way decent heads is an easy 1hp/ci cam.

What I’d have changed:
-Make sure it was an honest 9.5-10:1
-RPM A/G intake
-prepped/blended heads
-small street solid lifter cam

I’d have been looking for over 400hp out of that.
A hyd might get you there if the lifters were cooperating.