Ford 9" with Disk Brakes vs 8.5 & Stock Drums Length, Any Wheel Back Spacing Differences?

[GNVYUS 1]

I'm going Moser 9" with rear Wilwood 11" disk brakes, but the only spacing issue I can't seem to figure out is....

I have 15x10 (4.5bs)
325 tire is 13.2" section width
7.1" and 6.1"bs current wheels.
I'm at least 1" bs away from fitting them in squarely with the frame notch.
I can have the 9" rear end shortened by 2" total and get the spacing I need but the disk brakes vs drums add another variable.

Factory 8.5" with drums length
Vs
9" with Disk Brakes length

Are the disk brakes shorter in total length, like they trim say 1/2" each side vs the drums?

I'm thinking yes which would mean the wheels tuck/back spaced more and then I'll need a spacer.

Thanks for any insight, cars at suspension shop and swapping rear ends hit me this week, 850tq hooking 325 Street R on the factory 8.5" sounds like another Summer lost when it blows apart tuning the 2 step launch rpm.

 

[Chuck Leeper]

The shop should know to put the wheels/tires you are going to run under the car, squared up, and measure the mount face to mount face.}I use a fixture that replicates the rear axle to position the wheels}.
I would also consider, should the hsg be shortened, that the pinion be put as close to centered as possible.