you need 7.5 gears !
those are just gears ,it will not make a posi out of it .
just weld up the spider gears ? and make it a locked rear .then buy a 8.8
and buy good parts for it !!! when the 7.5 breaks!
No, don't weld the spider gears on a street driven car.
If you want a limited slip, you need a 7.5 limited slip carrier (probably easiest to find from a Thunderbird), and then you can also swap in whatever gears you want when you swap that in.
Yes, Ranger 7.5 in gears and the differential will fit in your 7.5 inch Mustang axle.
The same axle shafts fit 7.5 and 8.8 in Mustangs. Only one side from the Ranger is the right length, but if you get two of those, you have the 5 lug swap.
The 7.5 will stand a lot, one of mine has several hundred strip passes, has run lots of 12's, and has had a couple dozen launches on spray with Drag Radials.
It's in an automatic equipped car, and I am careful to lauch deliberately, but it has worked fine.
You can go with the 7.5 until you break it, or round up the money, and or, an 8.8.
I do have three 8.8's ready to go, just in case....
I see that the u-joints on 7.5 are the same on a 8.8. Can I get an 8.8 to bolt on to my 93 2.3l? I'm in the process of learning what I need to do a 351 stroker swap.