I have 3:55 gearing in my 67 Barracuda that is equipped with a 727 transmission - no overdrive.
I cruz at highway speeds 55-70 mph frequently. I dont see the issue with it.
Highway cruising speeds here in CO are 65-85 mph. Driving to the track (road course, PPIR) in my Duster I spend most of the drive at 80-85 mph, with a 904 and 2.94:1 gears it's right around 3000 RPM. I have a 3.55 gearset to swap in but I don't feel like being stuck in the "slow" lane the whole time and having even worse gas mileage on a 150-mile trip.
