On a similar note, I just pulled the timing gear, intermediate shaft(nut version), bushings, bearings, countershaft, and thrust from my '78, and dry fit all the corresponding parts from a late version '83. They look radically different but fit up just fine. Oil passages were added to the front bearing and shaft to improve lubrication. The inside and outside diameters of the relevant bearing/bushings were also adjusted for the larger diameter of the late shaft which used a bolt to fasten the timing gear as opposed to the nut from the early model. I'm confident it will work and reassured by the FSM which states for repair purposes the late version can be used if and only if the entire set is replaced(gear, shafts, and bushings, and fasteners). I am keeping the early diaphragm pump.