I wouldn't worry about 10.5 to 1 compression ratio on any aluminum headed Mopar, especially on any hemi motors that have not been CC on the actual dome volume in the cylinders twocents
Hemiroid motors are a completely different animal when it comes to true compression ratio scope
I've seen hemi pistons with advertised dome volume have 15 CC less when actually measured rant
Depending on the stroke and bore size that can mean the difference between 12.2 and 10.8, the bigger the motor the harder it is to get the compression up on Hemiroid whineywrench scope

Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)