Center housing replacement

I have a 1957 Massey Harris MH-50. Apparently a tooth broke on either the pinion or ring gear and the broken piece got lodged between the ring and pinion and split the center housing. I found a new center housing including pinion and carrier assembly. Now, the replacement center housing has 7/16" axle assembly attachment studs where as the original housing had 1/2" studs. No problem, scrounged up some replacement nuts for the different size studs and the smaller studs made it easier to get the axle assemblies installed. I installed the right axle assembly first with a paper gasket and aviation form-a-gasket. Snugged up the nuts. Installed the carrier assembly from the left onto the end of the right axle. Worked it around until the ring gear meshed with the pinion gear. Dry fit the left axle assembly into the carrier and center housing. All was good until the left axle trumpet got to within 1/8" of being tight. If I snug the nuts, the pinion and ring gear bind. If I loosen the right axle assembly, and try to snug up the left side, the ring and pinion still bind up. Is binding caused by the different sized axle attachment studs? What can I do to make this work?