Speedo Cable Help PLEASE!

I think you need a speedometer drive unit (the piece that fits on the trans & the cable screws onto) from a '66 or later car (but earlier than the '77 unit you have). I'm pretty sure that's the year they changed to the later style speedo drive. You should be able to find one in a salvage yard. It should be the same as a lot of AMC stuff, since a lot of those used a Mopar auto trans. I think I even found one on a Jeep transfer case one time. You'll have to make sure you have the correct drive gear to make your speedo read correctly. This varies depending on the rear axle ratio & the diameter of your rear tires.