hey man there is a very good place here in baltimore. i know its far but he specializes in heavy duty drivetrain work. i've never needed a d-shaft lengthened, but have gotten parts from him and had my d-shaft balanced there. if you want the number or anything let me know... or you can look them up online for a number.
Perry Hall Power- Ron Hash(owner)
Pulaski Hwy
Middle River, MD