I picked up my D60 FF for $500 out of a 2001 E350 and despite it being advertised as excellent condition w/ 110,000 miles, when I pulled the axles everything smelled cooked. I went ahead and replaced the differential ring and bearing, pinion and wheel bearings making sure they were either Spicer or Timkin. I used the Dana Spicer BOM lookup table to figure out part #s. I also replaced the axles with 35 spline and added an ARB locker. It all adds up but still less than half of what it would be to source an axle from Ujoint or Dynatrac.
2005 E350 RB 6.0 PSD for extended fun
1989 Landcruiser FJ62 for local fun
2011 VW TDI Golf for hwy fun