Hi 71 , my buddy has a 70 challenger with a 440 , 4 speed , Dana with 4.10s . Rear tires are 255-60-15 or G60-15 . Spins exactly 4,000 RPM at 70 mph . He gets passed by ricer cars and mini vans and HATES driving it on the highway !
Cars with that setup were designed for the 1/4 mile. Completely unpractical on todays’s modern highways.
The speed limit on today’s highways is not really any higher than 1966 to 1971.
He gets passed by ricer cars and mini vans and HATES driving it on the highway ! 
