Off what engine was the C6 taken? If it's off a gas engine, it won't fit (different bellhousing patterns), and I'm not sure if there are bellhousing differences among the diesels.
Regardless, you're going to have all sorts of issues, as the E4OD is totally electronically controlled, and the C6 is totally vacuum controlled. The computer on your '94 isn't going to like it.
It would be a lot of aggravation for a lesser tranny.
-2003 E250 cargo 4.2L V6, 4sp electronic auto, 22 axle (work van)
-1993 F250 XLT xcab LB 351 2wd E4OD 4.10 open (parked, tranny issues)
Probably the greatest harm done by vast wealth is the harm that we of moderate means do ourselves when we let the vices of envy and hatred enter deep into our own natures.