As a teenager in the 1930's, my friend's dad extensively modified his Ford Model T and installed an entire 2nd transmission inline after the first one. You can see the 2nd transmission's gear shift in this photo (Model T's didn't have stick shifts)
From:
http://ecomodder.com/forum/showthrea...odel-t-92.html
This gave the car 7 forward speeds, and 5 reverse.
Junkyard transmissions are probably pretty cheap.