Ok, I'm mid-swap and ran into an issue. The driveshaft for the legendary 1/2 ton factory Dana rear is about 2 inches to short. My question is, what years can I pull a 9 inch driveshaft from? Does it have to be 67-72? In know the track width is different for 73-78, but is the driveshaft any different?

 

if you have the yokes for both ends find a driveline shop and have them fab a new driveline.

 

HFM/M-Spt
Generally speaking wheel bases of 73-79 F-100 & 150s are +2" longer MOL model for model. IOW a 117" SWB in a 67-72 should be a 119" WB in a 73-79, and the 4X2s use the FoMoCo 9" as the OEM rear axle assy.

FBp

 

A new driveshaft will run between $250.00 and $350.00 to be built.
To cut down a driveshaft a shop will charge between $50.00 and $80.00 to cut and reweld if needed.
I would try to find the correct length driveshaft or find one with good yolk splines that is a little longer and have it cut down for your truck.
9 inch rearends were more common in the 67 through 72 trucks than the Dana 44 so a replacement shaft should be out there.
Good luck.
Ken