Since I am running with the stock 223 six and 3.92 rear, about the best I can do is 60. I would to eventually replace the rear with a lower ratio that would allow me to cruise at 65-70 with less RPMs on the little six. Are there rears from ater model F100s that would work as a direct replacement without any modifications? Appreciate the info.

 

there are some I'm not sure of the year however, I think there are 57 - 72 F-100; do a search for rearend exchange. There has been quite a few questions on this topic over the past couple months.

 

I just finished installing a 1971 f100 9" in my 49 f1. Same width. What you need to do is to try to get the axle/U bolt plate with the rear end and new U bolts. The shock mounting bracket needs to modified but that is easy. Your original equipment stock brake hose will even fit. You will also want to pick a pair of axle shims to adjust the pinion angle.

If you do a search on here there are several awesome posts on the subject. Good luck.

 

As staed above a 9" rear is almost a direct trandplant. You would probably want to find one geared at 3.25 for good freeway cruising!