C6 or E4OD would both bolt on. E4OD needs an electronic controller. I think a C4 from a car with a 302 would also bolt on, but probably not a good choice in a truck.
If you are swapping transmissions you might need to alter or replace other parts. For example, the shift linkage may be different or backwards on a new trans, or the overall length of the trans might dictate that you need to shorten or lengthen your driveshaft.
The path of least resistance is going to be to find a trans that is the same as what's in there now. Or have your current trans rebuilt.
81 F150 Flareside, Edelbrock Pro Flow4 FI, hydraulic roller 351W, E4OD, 4x4, BW1356
92 F150 RCLB 351W E40D BW1356 mostly stock