My 69 conv. has 455 ,T400,and an open 279....At 70mph I run at 2800...Mine is a 4 day a week driver and some highway cruises... I don't bend it around corners ,but with 500 lbs./ft. of twist ,I can get on it pretty fine....On trips ,I get 14-15 mpg , with the top up...but who puts their top up ? Someday I may get a posi rear as I light up my one tire at stop lights at times....Bear