Thread missing? 8-3/4 housing end as welded for shortened housing...

You do realize that just because the housing end isn't perfectly aligned with the tube doesn't necessarily mean it was done incorrectly, right? To me, that's a sign that whoever narrowed it most likely used a proper jig and did it correctly. I've done a few using pucks and a straight rod. They were all off by at least 1/8"-1/4". At some point, it's probably worth straightening the housing, but I never have and they all worked great and the axles slid in like butter.
Yup....I put the bar through the 'dummy' bearings in the carrier and then place the bearing housings on the bar. I then tack weld them on and recheck and if they are still on the money, I place more but larger tacks and recheck and if good, it gets 'stitch' welded. 1/2" long stitches and let it cool and recheck. If good, solid welding commences and then check again. Any misalignment after that is usually pretty minor and for the ones that are off a bit, straightening with a little bit of heat usually brings it in.