...No picture? I assume the Bearing and shaft would be Mounted in a press and the bearings pressed together, pressing on the Inner race. Then Mounted in a Lathe, 'Between Centers', and the Shaft is parted off to length, leaving a shoulder for the Hub to seat on the Shaft, as is Original. Then the Housing neck, that is cut down to your measurement, must have the Inside diameter Bored with a 'Boring Bar' (in a Lathe) to your measured depth, and with a Shoulder to 'Hold' the Twin Bearings in Place and to the measurement!! You'll have to mount and dial-in the Casting on a Lathe 'Face-Plate', to bore it, or on a Mill using a Vertical boring head, and dialed-in. When pressing the Bearings, Shaft and Seals back into the Casting, you press on the Outer Race! And, don't forget the 3 different Sealants! You would Not use Lube on the Bearings to Press-in.
Your problem, after all of this, will be, trying to get the Seals to actually SEAL!
Good-Luck with it.
See my next posting with a Photo and explanation.