Yes, I managed to get it together without damaging anything. I started "collecting" all the SM420 NOS Internal parts ( except cover ) back in July 2015. Looking back I really got caught up in identifying, locating, and then buying the parts. It sort of became as addiction I think...but hey, it was fun. In reality it looks like the only parts I actually needed for the repair was the countershaft, the reverse idler gear and the mainshaft and of course the bearings and gaskets. Since I have all these parts, I might as well use them for the rebuild. Starting on the mainshaft tomorrow.
