Guess it pretty much is going to depend on what you have for cam, convertor, gear and tire . . .

In my 74 Duster360 with 727, have swapped out the original 8.25 rear end with 3:55 for a 8.25 with 2.45 !!! Cruising at 70mph all day, running 2600rpm (about 23mpg at that speed too!). . . 360 has tons of torque to roast the one tire . . .

70 Sport Satellite with 360, 727, 3.23:1 . . . no tach, so not sure of rpm, but runs 75 - 85mph all day, no issue . . .

Now if the car is a 4:10 rear end . . .RPMS for sure !!!

Build it for what you want/how you drive . . .

Cheers,

Mark