No, the shaft doesn't extend all the way through the back...there is actually a freeze plug there.

I believe the hole is about 15mm. It wasn't really possible to get the calipers in to measure the hole, so I did a ballpark measurement of the freeze plug in the rear. The bushing is smaller than the diameter of the hole, but the viscosity of the epoxy made it easy to center. I also used 24 hour epoxy so, as it cured and thickened, occasional rotation of the shaft would help center it.

I personally didn't want to try to drill bushings to the correct diameter, just so I'd know that I'd have a nice, accurately machined bushing surface.