Whether you notice it or not will also depend on your gearing and stall.
But, if your cam has an idle lope, then it is probably at least as big as the stock 340 cam. That cam had only 44* of overlap, yet in stock form, headers seriously woke up a 340.
Log manifolds will kill the overlap, in addition to killing the inertial tuning.
But if yur running 3.23s, you won't hardly notice it until close to 60 mph in Second gear. Well except for if you don't have a hi-stall, then it will get doggie off the line, too.