I have 3.08 gears under my '55 1st. Its a GMC 270 with an SM420. It runs down the road at the legal limit with ease until you put a loaded trailer behind it.

I'm not expert on '67 - '72 pickups, but 2.92 gears doesn't sound right to me. Once you have it in hand, I'd check the ratio manually.

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...