Thank you all for your quick responses! What you all say makes sense. The Avid BB7’s are a SRAM product, so that could be why the adjustable washers are on both sides of the caliper on that ride. The Shimano XT’s have nothing in the rear, but adjustable washers under just the heads on the front. I will install the E350’s without any at all and check pad alignment.

The new 2018 Surly ECR has their unique Gnot-Boost rear horizontal drops and a sliding front/back caliper mount slots for pad to rotor surface matching to avoid misaligned pads, so I have adjustment there and the right/left slot on the caliper itself. If all the brackets are straight, I think I will be fine.

Cheers all and thanks again for your knowledge.