Once we got that far, the work really got rolling. The old axle and springs came out as a unit, the frame got stripped/painted over the axle, the driveshaft got new u-joints and a nice coat of paint, and the new springs went in.
The u-joints turned out to be a pain because the parts listed in the book were incorrect and the modern "HD" parts didn't fit. The front (at the SM420) ujoint was a 1350, the center (at the slip yoke) and the rear were 1310s. Conveniently the jeep axle used the same ujoint as the original chevy axle so no conversion was needed.
Once all the pieces were assembled, it all bolted up really nicely with new ubolts and plates. The pinion angle looked a bit off, but I thought maybe it was just because the axle was hanging from the springs...
Once it was on the ground it became apparent that the pinion angle was waaaaaay off. I had made the (incorrect) assumption that the spring perches would be level at the installed ride height. Turns out, instead of the pinion being 3.5° up, it was actually 5° down. So that had to get fixed. Out it all came again.
Once the axle was back installed with the correct angles, I put all new brake parts on one side and my daughter put them all on the other side and we buttoned up the back (for now).
The new wheels look fantastic and the ride height is perfect with the combination of new springs and proper axle installation.
