Be careful about WHICH shoebox rearend you get, FD. There were two. I don't have my book in front of me, but the cars that came without the overdrive had a much lower speed (about 4:10 to one) rear end. They'll cruise about 60, maybe 65 MPH with your flattie.
I have the higher speed rear-end on my shoebox with the overdrive, something more like 375:to one, and it cruises nice and easy at 70 plus MPH. Aint gonna set any time records getting there, but it handles the level freeway at that speed.
I was lucky and able to find an old Hone driveshaft overdrive for my F-2 that is really the best and easiest for the pick-ups. You just split your driveshaft and hang it on a carrier and when engaged the rear shaft turns at 33% faster than the front.
Cats meow, but good luck find ing one. They were aftermarket and kinda popular in the late 70's, early 80s in 4-wheel drive pickups...slim
