Anyone know by chance if they interchange? Lost an ear off the rear end in our 99 and we have an 89 sittin up on the hill. Probably a long shot, but i figure it cant hurt to ask.

 

There were at least two different designs for the yoke on the 10.25, something about long or short pinion? or bearing difference?
If the 89 has the upgraded version, maybe it will swap. Its not that bad to pop them both off and see what they look like at least. But my answer is a pretty wild guess as well so....?

 

Ford 10.25 & 10.50-Inch Axle Tips - Four Wheeler Magazine

not sure what the '99 uses for a yoke.perhaps just the same as the 2nd gen? doesn't say there.
but i sat an '89 like yours (the first gen) in place of my '93's (2nd gen) and just had to get the yoke straps instead of using the u-bolt style,along with a conversion u-joint.
my drive shaft was long enough still to slide out of the t-case slip yoke into the now shorter yoke on the year without issue.
so im sure you could figure something out.
you'd have drum brakes again and have to fix up the e-brake,then you'd have to use your older rims on back and run the newer style up front.
you could make it work probably,unless someone knows something i don't about the newer (what would be 3rd gen sterling.) which would be no surprise there,as i know nothing other than what that link says about the 3rd gens lol.

that said,i can't imagine a '99 srw sterling being that hard to come by.
i didn't even want to go purposely to a 1st gen,but i come to find 3.55's were just not offered (not confirmed,but i hunted for hours on end all over the US by phone.no once actually ended up having one despite what many were listed as) in the 2nd gen drw pickup axle (only actually found 4.10's in the drw pickup version in the 2nd gens.) so i had no choice.

 

According to the specs. (pinion spline count and length) here..I would say they would interchange.

Ford 10.25 & 10.50-Inch Axle Tips - Four Wheeler Magazine