I have a chance to buy a three speed brownie box, 20% underdrive, 1:1, and 20% overdrive.

I really do not need the underdrive, but it seems like a decent solution to the very low gears in my '57 3600 for longer trips with the overdrive.

Are these decent set ups?
Fair price to pay?
Availability of the shift mechanism?

It seems I would have to mount it about where the original drive shaft center support is, then modify my drive lines.

I think a shifter should not be too hard to make, particularly if I do not have to use the underdrive.

What is the down side to these?
Weight, noise, weak?

1957 Chevy 3600

At these prices I want my gas 100 octane, leaded, and my windshield washed!