A bit out of context...gotta know the ICE's torque/HP/RPM curve...where you wish to be towing/cruising/etc in RPMs...the tranny gears you wish to likewise tow/cruise/etc at
Then the tire's rev's per mile factor all this
Take my 7.4L big block gasser. Max torque is attained around 1,400 RPMs and continues at that level till about 3,800 RPMs
Red line is solid at around 4,800 RPMs with a dash red line starting around 4,300 RPMs
Over sized tires by about 7%, so the indicated speed is slow by about that amount. Indicates about 65 MPH, but actual is a bit over 70 MPH on this image
A small block can rev a couple thousand RPMs higher all day where mine would blow up. A diesel is similar to my big block gasser
Gotta know where you wish your RPMs to be at while towing/cruising/etc...
