Just a thought you may not have considered. I put a 5 speed OD in my 77 highboy and left the 4.10:1 gears and I love it. You can keep all the utility of a real "truck" and I can do 75 on the hiway at about 2500 rpm.
will probably be a bit more expensive but it's a 98% bolt in if you choose the right parts
good luck!
Changing gear ratio 4.56 on a 66 F-250 - Hiboy
66 F-250
Thanks for the idea. We found 3.54 ring and pinion master set for $200 and my son does this kind of work in Waterloo. I haven't priced a five speed yet. Hey, if you know where I can find a 2bbl intake manifold for a 300 6cyl let me know.
Hal
Hal
Oldman