You stated the trany is a 4-speed manual with overdrive/OD, but the T-18 does not have OD. IF you have OD, it can either be a SROD or TOD tranny. Whichever of those models you have, they will have an ID tag/label on the driver's side of the tranny housing. If you don't see any label, look on the passenger-side. IF it has a square, bolt-on cover plate for the PTO output there will be a metal tag with numbers on it. Ford put all sorts of tranny and engine combo's in the 83-86 Bronco, some with the NP208 or B-W transfer case, and some with a Ford 9" or Ford 8.8" rear axle. IF you can determine what all of the drivetrain parts are in your 83, I might find the extension housing for you. I'm currently looking around for stuff for my 86 Bronco with a NP435 manual tranny and NP208, JSM84