I believe any 80 axle will bolt up. The only changes were ABS and the outer stub axle/ drive flange, IIRC they happened around the same time in or around '93. Later years got a different ABS sensor, but I think the plug for the wiring stayed the same and either sensor will work, but you might want to research that a bit more. I believe the sensors are interchangeable, so even if the wiring connections were different you could use your original ones. Your sig says 'Locked!', if that's factory then your options are a bit more limited if you need the 3rd member or housing. They use the same parts from the axle shafts out, but if you needed to change the housing and wanted to use your 3rd you'd have to do some minor surgery to make it fit a non-locked housing.
If I were you I'd be looking for a '94 or newer axle, newer the better just from a mileage (wear) standpoint. Older than '94 you'd want to make sure it has the longer axle stubs and drive flanges.
The birf end (stub axle) matters, sort of. It will either have an ABS ring or not. An ABS ring can be fitted to a non-ABS stub axle as far as I know. The issue then is that the splines on the end of the non-ABS ('91-possibly '93) stub axle would be shorter than a later axle. Of course, your truck being a '93 might have the shorter stub axle anyway. Either way, if you just need the inner axle you'll be covered. You might get a spare birf out of the deal, which is never bad. I'd see if you can get him to toss in the drive flange too, then you'd be covered for sure in the event you wanted to have a spare birf laying around.