I had a 1986 Toyota 2wd. I don't believe it had a tach and I think it had a four speed. It would go about 85 mph.

I had a 74 Datsun 2wd with a four speed and a tach. 40 mph in fourth was 2k rpm, 60 was 3k rpm etc. Had a 1990 Sidekick with a five speed that cranked about 4500 or so at 80. It would go 85.

In 1974 I bought a 1962 Ford Econoline that had the same small six that Ford used in the Falcon. It also had the same wheels, 13", and the tires were probably D78 13. I drove it thousands of miles with the 13" tires on it and according to the speedometer it got 18mpg. I replaced the rears with 14" wheels and E78 14" tires and, according to the speedometer, it got 18mpg. That doesn't establish a rule, but it is a data point.