Power Surge has a good point, from my old notes, from the back of the SHO block face to the flywheel mating surface on the crank(back of the crank) I measure between 14.85-15mm
1. Back of the SHO MTX flywheel mating surface to the friction surface, its 25mm
A. Breaking the flywheel down, mating surface to where the backside of the bolt head would touch the flywheel, its 12mm
B. Where the flywheel bolt mounts to the friction surface, its 13mm
C. So you add this up you get back to a 25mm offset flywheel from back of the crank to the friction surface
2. Transmission mating surface to the beginning of the input shaft spline its 31mm
So if you used a 1/2" spacer with a 1/2" adapter plate and everything lined up, you just got lucky. From experience, I used a 5/8"(16.15mm) adapter plate but the flywheel spacer ended up being about 17.5mm even the trans mating surface offset of 31mm to the input shaft spline was exactly the same as the MTXIV trans and using the same MTX flywheel. Most people would mount the starter to the trans. And for this I needed to 1/8" spacer (shim) to push the SHO starter away from the SHO flywheel.