Couple random thoughts:
Run the eight lug axles. u joint sizing will be bigger on new power train, creates a ******* drive shaft. Look for the solid front end, will be easier, but I think they were both D50s. I wouldn't shy away from a manual donor truck either. Your Broncoshould be somewhat accommodating of the pedal assemblies and your more likely to find a manual still in good working order, and yes PSD are fly by wire. Fire wall clearance may be aided with a1" body lift perhaps. not sure on t case fitment but I doubt their interchangeable. Get donor truck with trans you want and use provided t case. A Cummins weights every bit what PSD does, around 1,000 lbsą. Far as reliability goes, yes PSD can easily go the distance but it has a lot to due with how it's taken care of. And fluke issues can always arise over time. One thing I would look into as well is early PSD I think had mechanical lift pumps and an electric one was a common upgrade, may be use your in tank pump for purpose.