I pulled the axles from my '87 3.8L Thunderbird tonight in order to fix a leaking wheel bearing seal and found one of the axles had already been "repaired" and that the inner race (i.e. the axle) was spalled in both places. I pointed my browser towards coolcats.net and found axle interchange information on two pages that is inconsistent.
From here: (http://www.coolcats.net/tech/general/axleinfo.html)
1983-85.5 Cougar/T-Bird 7.5" and 1986-93 7.5" & 8.8" Mustang (4-lug) interchanges with 1983-92 Ford Ranger (5-lug) - 2 driver's side shafts or 1986-97 Ford Aerostar (5-lug) - 2 passenger side shafts
1985.5-88 7.5" & 8.8" Cougar/T-Bird interchanges with 1986-93 7.5" & 8.8" Mustang
1987-88 8.8" Turbo Coupe interchanges with 1994-98 Mustang w/ABS (5-lug)
From here: (http://www.coolcats.net/tech/advanced/4to5lug.html)
1983 to mid-1985 Cougar, 7.5" rear - 1987-93 Mustang-width axle shafts (aftermarket only); 1983-92 Ford Ranger pickup axle shafts (2 driver's side, ~29 5/8"); 1986-97 Ford Aerostar minivan (2 passenger side, ~29 5/8").
Mid-1985 to 1988, 7.5" rear - 1994-98 Mustang-width axle shafts (7.5" or 8.8")
1988 XR7, 8.8" rear - 1994-98 Mustang-width axle shafts (7.5" or 8.8")
The second page has been updated more recently and I think it is correct, but I'd like to be sure before I go trying to find replacement axles.
79-93 Mustang axles are too short - I can verify that from personal experience. A few years ago I had the exact problem you have on my '88 Cougar axles and the junkyard gave me Mustang axles. They were too ed short, which left me in a fix - I had the car on my hoist at the dealership I was working at, on a Saturday, and all of the junkyards had closed by the time I discovered the problem. I ended up having to put the car back together with the worn original axles.
94-98 Mustang axles are the proper length, but are 5-lug, which makes them not a direct swap.
To answer your question: The only axles that will properly fit your rear end are those from late 85-88 Thunderbirds and Cougars. No other models interchange. You cna try your luck withh JY axles, but be sure to look at them before paying for them - they likely have the same wear your existing ones do. I had to replace the axles in my 87 Sport too, and after checking out 7 87-88 T-Birds and Cougars at the local salvage yard I finally found a good pair. You don't even want to know what new ones cost (if they're not obsolete by now - they cost $700 apiece back when I did the Cougar in 1998!)
You should try a machine shop. Most work axles can be sleeved at a machine shop, so you might not have to replace them.
The sleeving is the standard procedure on semi truck drive axels every 5-7 hundred thousand miles (I worked maitenence for a local transport company last year) so I'd assume their are shops all over the place who can do that. You would have to bring them the axels and new bearings (unless they supply them).
FYI, I think it is Federal Mogul that makes "repair bearings" . I used them on my axles due to some infavorable wear on my axleshafts. There are a bearing and seal all in one, and relocate the bearing surface to the surface that the seal used to ride on. This is not a hack or quick fix, it is a permanent repair that is just as good as original. Just find a good parts guy and he should be able to get them for you. :)
The axle in question has already had a repair bearing installed and it too has worn down the axle surface. The pinion seal leaks too. I guess these things are to be expected with 212k miles on the car.
I upgraded to Moser axles when I went to a 31 spline rear, but these guys will make any length you need for $225/pair or $115 ea. in 28 (stock) or 31 spline. http://www.moserengineering.com/moser_interior/customaxles_cclip.htm I just told them my application and they knew what length (though there are length tables on the internet - you need to search for them). My order actually had another vehicle listed on it so there is a cross for the 4-lug TC axles. It appears that 7.5" & 8.8" use same axles from interchange info above?