See if you can get the guy to send you a pic of the parking brake assy. Most of the medium duty trannys use a seperate but self contained parking brake assy attached to the rear of the tranny. Take a look at some of the ones offered on ebay for ZF's; it is common for them to be a bolt on assy, and the bolt pattern is the same as an NP205 round(or np208, np241).
If it is this type, all you have to do is remove the park brake assy, remove the tranny mainshaft, and machine, respline, and re-heat treat it. Should be able to get this done for around $300.
The only real drawback to the medium duty trannys is they don't shift smooth like a nv4500 or a zf5 or 6, they shift like a dump truck should.
Jimbo