Aluminum heads are why newer engines are 10.5 to 1....real muscle engines had 11 to 1 with iron heads,,those are all history, I don't think any new engine has iron head--well maybe those semi trucks still do
Then again, in days gone past, there was also fuel to feed them.
My wife had an Oldsmobile with a 425 labeled on the pie tin reading "Ultra High Compression", "Super Rocket" & "Use Preimum Fuel Only" @ what I remember as listed @ 11-1.
Nice engine!