i had a 170 in a 64 dart. Single barrel, 1.25” exhaust. I could get up to 65-70mph and stay there. 70+ it could do but it wasn’t it’s happiest.
if you’re trying to race it, in factory form it’s just not built for it, but it’s a tidy engine when adjusted properly and it’ll perform well. I got good mileage for a daily driver.