When Ford started making their own around 1959, they used the two speed divorced Dana/Spicer 24 in both F-100-F250. The F100 switched to a single speed married Dana 21 around 1964 when they got the "pretty" bed. My 1965 F250 still has its original 24, and it is tough as nails. they used this case up to around '73 or so, when they switched to the NP 205 in both, still divorced in the 250's with the manual trans up until 1977, married cases with the automatics when the C-6 finally became available. I am a litte uncertain on the exact years, so anyone feel free to comment.
Thank you, BillBallinger. Sorry it took me so long to reply to your response. I just got a F-100/F-150 book that says the F-100 had a 2 speed transfer case up until 1965, in 66 the F-100 got a 1 speed transfer case.