I know I'm late to the party, but the 9.75 axle from an Expedition of the same gen is the way to go. Plenty strong. And inexpensive.
This is my exact logic. The expedition 9.75 used a 5 lug axle which is the same as the 1997-2002 F150 (our truck) but with a 3/4 ton axle bearing and massive rear disk brakes. The only difference is the expedition was coil over. AND the parts are CHEAP! We paid $200 for a complete axle with brakes.
The 2000-2002 F150 had disk and a 8.8 or 9.75 but the small axle bearings. Newer F150 uses the same 8.8 or 9.75 BUT with the 3/4 axle bearings but is a 6 lug so it would need $500 custom axles. Full floating 10.5 is way too big and the front and rear wheels will never be the same. 10.25 axle uses the same axle bearing as the 9.75 but is 8 lug once again requiring custom axles.
The most bang for the buck is the expedition 9.75 limited slip with the 3/4 ton axle bearing with disk brakes.
