A833 question

With 3.91 gears the final ratio with O/D would be .391 x .71 = 2.77.
with 3.55 gears the final ratio with O/D would be .355 x .71 = 2.52.

Back in the day, we always had, and still do, a set of 2.76 highway gears for trips, so I guess I'd recommend the 3.91 gears. The other side of the coin is the 3.09 first gear. 3.09 x 3.91 = 12.08 multiplied by the engine torque. The 273 would spin the tires all through 1st and second gear with 4.10 gears in a 64 Barracuda. I'd say a sure grip would be necessary. Tires are better today, but...