See how things are different? In 1960 I used to brag about my cruising at 73mph and only 2700rpm in my Austin-Healey 100 BN1.
As it happened (I think I'm remembering this correctly) that was exactly 2500 piston-feet per mile, the amount of piston travel considered the most-efficient and least-wearing, sort of a "cruise at this speed forever without worries" speed.
EDIT: As a kind of yardstick, the VW Beetle of that era had a theoretical safe cruising speed of 123mph. Not very many piston-feet per mile there, eh?
I have no idea what a contemporary Mustang's piston-feet per mile is, nor do I remember how to calculate it. Maybe Gooooogle will yield up something useful?
Well, there seems to have been a glitch in my memory: these guys are talking in terms of piston speed in feet per minute. I suppose that is convertible, some way.