Being slightly mislead already, here's some good info to set ya straight and some advice from someone doing exactly what your planning....
- 66-70' have narrow solid axles, Dana 30 and small bearing 9". They have the same track width as a ranger.
- 71-75.5' have Dana 44 w/ drum brakes and small bearing 9", again same track width as the ranger.
- 76-77' have Dana 44 w/ disc brakes and small bearing 9", again same track width as the ranger
- 78-79' have Dana 44 w/disc brakes and big bearing 9", Fullwidth axles approx. 6" wider trackwidth IIRC.
-All pre 80' 4wd F100's and F150's will have some variant of a D44 up front, disc or drum and varying ujoint size, and a 9" rear. The newer the donor truck you can find the better.
Now for the advice....When you got to do the swap, get both axles (Front & Rear) built as much as you can before you even think about swapping....I thought I'd use the cash from my heavier ttb drivetrain (D35 & 8.8) to pay off the build, but ended up goin way over budget, and the trucks been down now for over 6 months, and I'd like to let others learn from my mistakes.
-andrew