I recently purchased a C20 with a manual 4 speed. I would like to change the gears in the tranny to get rid of the granny first gear and possibly turn fourth into an overdrive.
You most likely have the SM 420 as mentioned. Your idea sounds good, but it probably won't work. They were converting Muncie 4-Speeds for a while and realized there were problems with it. When not needing the Overdrive and cruising around in 4th gear (the old 3-Speed position) it was wearing out bearings too quick. The trans was only in the "Direct Drive" position when in Overdrive. Besides that, I don't believe that anyone is making the gears that you would need. Someone with trans rebuilding experience could probably verify this, but I believe you would be better off with something like what Larry suggested.
Bill
