Re: Axle question
Your Bronco will have 31 splines. The 28s are pathetically weak. I've found a truck or two w/28 splines, but it was older (early '70s) F100s and 150s. That's not to say Ford didn't use 28 spline units later, 'cause I'm sure they did, even in trucks.
Once you've pulled one of each spline count, you can tell right away. The bolts are smaller, many things are noticeably different on the outside. I don't remember the specifics, but when I was in the process of removing a 28 spline unit I could tell something was amiss before I even had the axle out.