rear end pinion angle...

Original angle of pinion gear shaft is 3 degrees

That may or may not be correct for your application. You need to match the drivetrain angle (i.e.) centerline of crank shaft through output shaft of transmission. If your drivetrain angle is greater than 4 degrees, I'd suggest you adjust that to get below 4 degrees first.
You want shims that are no more than 2.5" wide, which are pretty much standard. Also cast aluminum seems to bend into the proper arch better than cast steel.

Good luck,