I'm running a 4.10 axle right now. I like the backwards 3 speed idea-I've wondered about doing that before. Seems like I remember my neighbor's Grandpa setting something like that up in his old Cornbinder tow truck years ago. He(and the truck)have long since passed on though,so I can't ask about it. Sure sounds possible,though. Once I have the Mack up and running,I can take some time on the '62 and get creative.
Going back to the backwards 3 speed idea-imagine if I hook up both shifting arms... grin grin
Speed

1954 GMC 350
1957 GMC 1/2 ton
1962 Chevy C-30
1952 Chevy 6400 dump bed project truck
'98 Harley FLSTC
'66 Pontiac Catalina
'76 Chevy 1 ton Duallie
'84 Bronco II
'78 Dodge W-200
'81 Toyota 4X4 truck