Ok I have the original TH350/NP203 in my 78 Jimmy and the speedo just went out on me. The part I need is actually in the T-case, but not the gear on the main rear shaft. The one I need is not the speedo adapter or the key that slides into the T-case, but right where that key slides in. It seams to be stripped !! Yes I know there are a ton of different ratios, but don't care !! Just need the speedo to read and then I'll figure out how far it's off. DOn't want to spend money on a new one when I am gonna change the axle ratio soon. Hmmmm 4:56's !!