If you've seen an F-250 from 80-87 with a solid axle, it was swapped in. ALL F-250's from 80-96 were TTB. In addition, ALL F-350's from 80-85 1/2 were TTB Dana 60's. They went back to the monobeam 60 mid-year '85.

 

The 80-85 F350's were D50 TTB's, same as a F250HD(well, the ones with max front GAWR, snow plow prep, and extended cabs.) And a D60 will bolt right in in place of them. The donor for my 86 was an 88 crew cab, so, I got some nice positive arch springs in the deal, probably picked up 4" of lift. And, my truck already had the holes for the panhard bar.
Thanks 8 Lugs, I forgot about the crossmember and driveshaft.
You may need to change the front output yoke on your t-case, as they upped the size of the U-joints on 5 speed and some auto trucks in 88. My truck had half ton sized joints stock(1310's), and the 88 had 1330's(proper 1 ton stuff.) Also, it's possible that a standard yoke mightn't be compatible with the CV joint on the F350 front shaft.

On the brakes, you're going to have to use the 94 calipers, they changed caliper mounting systems in 85, and then again in 93 or 94. Either way, your existing ones won't fit the mount brackets on the new axle.

The frames got 4" wider in 1980, not narrower.
Compared to a 78/9 axle, an 85.5-97 D60 has the differential offset further to the drivers side for crossmember clearance. I'm not sure about the perch spacing, but, I think the 85-up stuff is wider. Haven't dealt with the older stuff very much.

 

crazy4Fords, i will still have to worry about tire hitting the frame because i'm running 35x16 boggers with 4.5" of backspace which isn't enoughand not the the springs because of the narrower distance between the spring perches, but as far as i can tell i'm not going to any rubbing other than the frame, but my "home brewed" (with help from the offroad forum) 6" lift i will be doing in june will take care of that.

 

one guy that i know was telling me that ford used the same frame on the F-150, 250 and 350...myself, i find that hard to believe...he said that it's just a myth that they use different frames for each....what exactly are the differences in the frames??

MontanaFord