According to my calculations, with 215/75R14 tires, a 2-speed Fordomatic and 3.10 final drive, my Galaxie should be doing 2340 rpm at 60 and 2730 rpm at 70.  I assume the number is actually higher than that, given torque converter slip.  Am I correct in thinking that the rolling tire diameter is smaller than the theoretically calculated one I used to get those numbers as well?

Regardless, I don't feel good about cruising at 2730 rpm (or more).  It just bothers my conscience somehow; I can't help but think of the engine wear and fuel consumption incurred by running at such a high speed.  The engine is smooth and quiet even at 70, and doesn't exactly feel wound out, but even so I know it could move the car along more happily around 2000 rpm.

In order to do anything to change it, I see two options: get a 3-speed and change the rear axle ratio to something more like 2.7, which would bring rpms to 2040 at 60 and 2380 at 70, or put in a 4-speed overdrive auto such as the aod, which would bring rpms down to 1570 at 60 and 1830 at 70 with the stock rear gears (assuming 0.67 overdrive, as per Wikipedia).  Of these two, the overdrive trans is more appealing, because it's probably less work.  Though it may be more expensive.

Option number three is the easiest and the cheapest: don't change anything, and don't worry about it.  I prefer this option, but as I mentioned before, I have a hard time not worrying about it.

What do you guys think?

1954 Crestline Victoria 312 4-bbl, 3-speed overdrive