I would vote for a later model 9 1/4 Semi Float 14 bolt. You can find them in early 90's to 98ish ex cab 1/2 ton, 4x4 pk (6 lug of course). You might have to move the perches to fit exactly, but it is much stronger than the 12 bolt.
Nice trip report.
Jack
That is my vote too. They put these in SF 14-bolts in your old body style Burb, but they were all 8-lug. Not sure if you could do some combo of old body style housing and newer 6-lug shafts and drums. Probably easier to just move the perches on the later model 6-lug SF as locrwln suggests.