I've done some more calculations and increasingly I'm not convinced I can save enough fuel to justify spending money on any overdrive transmission, when I already own the TH 400 and TH 475.

I may give up this whole line of thinking and just go with what I've got.

1955 1st GMC Suburban | 1954 GMC 250 trailer puller project | 1954 GMC 250 Hydra-Matic | 1954 Chevy 3100 . 1947 Chevy COE | and more...
It's true. I really don't do anything but browse the Internet looking for trouble...