Ported 452 or Edelbrock RPM

Regarding steel gaskets, I talked to a buddy of mine that services infinity cars and he says all v6 engines have steel shim head gaskets from factory.
He gave me multiple examples of other modern cars that also have them also.
So far no leaks in my case.

But I have another problem, vibration at high load.

My trans angle is 2 degrees down in relation to the ground, rear end is 1 degree yoke down. I have SS springs and pinion snubber.
I put 4 inch shims today as this is the only thing I had. Will test tomorrow.
How much twist is possible? How many degrees up can my rear end go under load?

I guess I will need to find a better topic for this. Can any of you guys suggest something?
Shimmed it looks like in the photo.
Seems a bit crazy, my understanding is that in irder for it to be good, rear axle would need to twist up by 7 degrees to end up parallel to the transmission that is if transmission angle remains unchanged which is not the case I bet.

8A1DEEF1-3C82-46EC-A714-521F5E07EA4C.jpeg