9in axle length

A 10.5" wheel? Is that from edge to edge or the actual bead?

I have a spreadsheet that will give a really good axle length to center a wheel in your tub. According to my sheet based on your wheel width and backspace numbers, the total width (with rotor hats) would need to be 51.75" to center the wheel.

Dr Diff has a calculator on his site for a 9" using mopar pinion offset. Based on your numbers 50" total axle width sans spacers, I came up with 45" for the housing.
The axle lengths you came up with are for a 45" total width 9" rear.


You might want to double check the bead width and total width of wheel. Get those number and I can re-run them.