I pulled this SM420 from a big 1960 GMC truck at the local junkyard. Still had all the original 2wd tailhousing and e-brake setup so no I doubt the mainshaft has been changed or modified. I'm not sure if the age of the 420 has anything to do with it.
I had a 3spd TC bolted to it for a while, but never really finished the install and decided to go with the Toybox/Splitcase instead when the $ became available. We are about 30 months in to a 12 month build
Yes the LC 3spd input gear goes right on now after all my polishing/deburring. I tried for two days to get the Toybox to slide on and kept convincing myself that I still had a burr or it wasn't aligned just right. It just starts to go, but I think that is the taper on the shafts as they align. Then it gets stuck and I have to carefully pry and tap it off, even though I've coated it with 80/90 to lube it.
