I have a 1978 f-250 4x4.I need to know if a 2 wheel drive 4 speed trans can be made to work in my 4x4  

Yes, my granpa has a 75 f250 with a devorced tc. The thing is tough and I mean danm tough. Not sure what kind of tc though but it does work.  

While I am not quite sure here on Fords, GM has long used a heavier tranny case in trannies meant to be used in 4x4's to be able to handle Tcase counter torque. So short of divorcing Tcase, you do not want to swap tail shafts on a 2wd tranny and use it in a 4x4.  

Well, all I know is that granpa's devorced tcase works very well and is very strong. I don't know what engine, gears or tire size you are running, but I know he has a 425hp 390, NP435, 4.56 gears w/ lockers, and 40x17/16.5 superswampers. He goes crawlin, muddin and rides the dunes all the time with NO tcase problems in his Ford. Maybe it's just another GM problem.  

A divorced Tcase places no counter torque problems on tranny in low range because it is not attached to it and it restrained by frame mounts. When Tcase is bolted directly to tranny it is a different matter.