Yes, the Ford Bronco had the 9" rear axle with 31 spline axleshafts; however, they are only certain years......unsure of what those years are though. I'll check on it and post when I found out the answer. Late
OK well I checked on the 9" specs and I have some conflicting information. It seems that it was available up to 1986, then it swaps over to 1988 which states those years as having the 8.8" rear
To Sum it up:
--up to 1986 had the Ford 9" rear axle
--Starting in 1988 the axle switched to the 8.8" rear axle
***I don't know what axle was used for the year 1987, if anyone has any info on this it would be greatly appreciated!!. Let me know if I can be of any more help, take it easy man. Late.