Ditto...

I would be looking at a fuel supply issue on the big end. I have had it, as well as many of my friends. Pump might say 140gph, yet you will find, it just might not be enough.

I had a 340 car with 3/8" fuel line and such, jetting changes made no difference in mph, car would not climb much past 1/8 in high gear only. It had a holley blue on it. I put a second one inline with the first....From one pump right into the other and up to the carb. I dropped 10 jet sizes, and mph picked up big time.