ProComp/Speedmaster aluminum heads

I'm pretty sure I have Crower Springs and I remember something about 350...

I don’t think you’ve grasped the idea that “most” springs designed for use with OE SBM heads are going to be too short to properly fit the new heads.

Forget what the catalogs and “specs” say.
The springs are what they are......regardless of the what the specs say they are.

Have both sets of springs tested at the installed height of the new heads.
The old springs are either suitable for that height, or not.