I've decided this thing needs to drive on it's own-- either to help my motivation to work on it, or to make it easier to sell to the person who's going to finish it.
So I set the pinion angle for a single-ujoint driveshaft, and visited GRS to get the stocker shortened and stuff. Turns out there is no conversion u-joint for what I need, and the closest thing that exists is a 1350-1410 unit....which the guys at the shop said is junk, and I don't want it. There is no 1410 yoke to go with the 2.75" driveshaft tube.
So as usual, I had to make my own thing. A couple chunks of axle tube welded together made the adapter I needed.