I changed the front half of the transmission cover on my '62 C10. I had the low hump for the 3 speed, but a previous owner had installed the 4 speed (SM420). Since it didn't really fit the low hump cover, they just bent up some sheet tin and screwed it on.
Since I wanted to do it right, I located the correct pieces for the high hump cover and cut out the low hump firewall piece. I glued the firewall half in with a spray on rubber undercoating.
I don't know why you couldn't weld in nuts on the engine side of the firewall, and drill matching bolt holes on the firewall cover. Then you could bolt it in like the C70 you got it from. You would probably want to bolt the transmission cover to the firewall piece, the bolt that assembly in to line it all up before you drill for the new bolt holes.
You've got me thinking I may want to do that the next time I have the cab gutted. I haven't done that for a long time, but I will need to do it before I tear down for paint. No telling how long that will be though.
Thanks for the idea!
