Will this rust on gears be an issue?

Considering the application, I decided to look around for another set of gears. I found a pristine looking set of Chrysler 3.23 gears. I will be getting help from a friend to set up this coming weekend. From readings about used gears, I have learned to set up focussing on the coast side pattern. Is this correct? Any tips or advice about used gear setup greatly appreciated. I have a complete new install kit, and crush sleeve eliminator.

Can I modify my old pinion bearing to use as a setup bearing by clearancing the inner diameter slightly?

I will save the other ring and pinion with the slight rust for the 318 Scamp.