47-55.1 Rear End Advice Needed

[dsraven]

if you are gonna swap the axles then you might as well start with something that will hold up and is fairly common. the 8.8 ford fits the bill and is only marginally different than the chevy 12 bolt as far as ring gear diameter and pinion size. there is the lug pattern difference but that can be overcome fairly easily. if you want a centered middle section then try finding one from a mustang.
I have an explorer axle in a 57 chevy truck frame. it came with the larger axles, 3.73 ratio, posi and disc brakes. the park brake is easily configured. to overcome the wheel bolt pattern issue I simply grabbed an extra brake rotor when I got the axle from the pick n pull yard. I cut the brake surface off the rotor so all that was left was the flange that fits over the actual axle and has the holes for the wheel studs. a friend of mine has a metal lathe so he chucked it up and marked/drilled some 1/8" holes in a chevy pattern in the area in between the ford lug pattern. this became my template/pattern. then all I needed to do is bolt that template on the axle using the ford pattern, mark the axle flange using a 1/8" drill bit through the predrilled holes in the pattern, just a small mark is all that is required so the template holes don't get rounded out. then I removed the template and the axle from the housing (I was giving the axle a good flush and check over anyway so the diff was coming apart no matter what), with the axles out it was easy to center punch and drill the new chevy pattern holes in the axles. with that done I also laid the template against the brake rotors and marked/drilled them for the new pattern as well. when drilling the axles I used chevy wheel studs the same size as the front, mustangII, brake rotors so the wheel nuts are the same size and wheels could be swapped front to rear with no concern for wheel stud hole diameters. the pinion flange will look different than the chevy yoke but that is also fixable because some broncos came with the open ujoint yoke style flange. there are several options available in different strengths and sizes. if you grab a diff from the graveyard it would be a good idea to dissassemble, check and rebearing while it is apart. there are kits available with everything you would need.
if swapping axles ensure you don't overheat the axle tubes when removing brackets or welding on brackets. the overheating can cause the axle tubes to bend as they cool off. then all your work is for naught.

bearing and seal kit example. not sure of the quality, just an example
https://shop.broncograveyard.com/88-...uctinfo/32319/

here is a link to the hotrod network mustang axle page
https://www.hotrod.com/articles/ford-rear-axle/

here is a link to the pinion flanges available if you want to use a 1310 or 1350 series u joint instead of the bolt on flange style that usually comes with the 8.8 axles

1350 yoke
https://shop.broncograveyard.com/For...ctinfo/32355A/

1330 yoke
https://shaftmasters.com/fo88inpiyo13.html

1310 yoke
https://eastcoastgearsupply.com/i-57...bolt-yoke.html