Caster is more important than the pinion angle.
Stock 1310 and the stronger 1410 have the most angle capability. Add on a xx10 Tom woods offset ujoint for the best scenario to prevent ujoint binding with droop.
As for shims if you choose, this 60 uses studs in the housing so you’ll need two shims on the diff side to set the ubolt plate square again. So three total for the front axle.
6 degrees caster is about gm spec and ideal, but general consensus here is 4 drives good also.