[49studebaker]

I have been looking into the same issue. From what I've read, the newer 700r4 has a sleeve over the tailshaft that has the electronic speed pickup on it. I believe Redneck is right, just slide that off and you'll find the grooves for the old type speedometer (retainer clip) on the shaft. It seems either mech/elec. will work with either shaft, you just need the proper retaining clips,etc.