Okay..... I come up with 7.5:1 with a 90cc head and pistons down the hole .155...... close enough.

If you milled the heads .060 and ran a shim gasket it would raise the CR by one point.
A little different cam, 2 hrs bowl blending, 1-7/8” headers....... shoot for an honest 450hp.

If they really used 2” headers for that test....... there was probably a little power left on the table.
Smaller tubes should have pumped the tq numbers up....... and since the hp peak is at such a low rpm...... it usually ends up that if you start with a higher number(tq), you end up with a bigger number(hp).