when Dr. diff sells the 1inch offset hangers for the B body rear he recommends the shim package to adjust pinion angle.
And it's a good idea to check the pinion angle but I've done the conversion three times & never needed a shim.... Never bought a kit either, they weren't available back in the eighties & nineties...
Yes it's always a good idea to check the pinion angle. I just swapped straight across, no shims needed. The pinion angle is fine on my car. I'm pretty sure the perches were at the same angle on the B and E bodies, I know the A-body perches are different, but it was like 2 degrees if I remember correctly.
Keep in mind too that any time you change the rear ride height you need to check the pinion angle as well, that's one that most folks miss.