You are correct SM420 granny first gear. We thought the SM420 would be an easy install and are avaiable.....Are there any three speeds that would be recommended? Three speeds seem a bit harder to find any suggestions would be very appreciate.

The OD is a great transmission as long as you know its quirks. Just too much BS with all the cables, solenoids, and kick down swithchs. My wife hated it when it was working. Also try to get one fixed. I have been to 27 transmission shops in a 200 mile radius over ten years they all laughed. Enough ...i just want to drive 55 and survive.
Thanks, Steve