It's easy to swap an 8.8 to 5 lug, you could also go install the fox body 4 link in your car. Theres a few companies that make kits for it.I was also researching it and I guess the foxbody 8.8 is the same width as a 67 8in and 9in. So with brake line modifications and adding leaf spring perches you can install it in a classic mustang. Just not sure if it's worth the hassle lol. Foxbodys are 4 lug so I would have swap out axles as well.
Side note, you can run the newer (up to 04) 8. 8, just need to swap the axle shafts since they are wider due to the abs rings. Housing is the same though as a fox if I remember right.