Nice pics of the tire differences.
I got impatient, built the axle and mounted a set of tires to adjust the diff a bit. Now I know I'm out of rear axle shims, or put them in the wrong kit. I had enough regular and flange bearings for the height adjusters and diff. I had a Kimbrough 48P 75 laying around. It should give me a good starting point for testing indoor. I have some 78 spurs on the way.
Daring to dream.