if your current front axle is a D50, the hub,rotor and locker will transfer over to the D60
E350s don't come with a D60 front from the factory, every single one of those is a conversion job of some sort or another. Some people have successfully used E350 rear axles under their F-series trucks, IIRC the normal van-body (as opposed to boxes like U-haul's) vans have the axle perches 1/4" off (per side, so 1/2" total width difference) when compared to the trucks - the spring and shackle bushings can usually take that misalignment, but measure just to be sure.Sterlings are easy enough to find but I cant even find a 1 ton being parted out. Theres some E350s available but I don't know if I could use those front axles.
There is a D44HD that is also TTB with leaf springs. Take a tape measure and measure from the pivot bolt of each beam to say its lower ball joint, if both sides measure the same then you have a D50 front axle - the D44 has beams of unequal length IIRC, driver-side being somewhat longer than passenger side. Front GAWR from your door jamb sticker could also be a cue as to which axle you got. But AFAIK all OBS with a diesel should have D50s regardless of cab style, it was the bricks and older that only got the D50 if extended cab OR special order with one as a plow package or whatever.A D50 is a TTB with leaf springs, right? Or is their another difference?