For a streeter, The cam and gears combo will pretty much dictate if the headers are gonna be a big deal.
IIRC the early 340 cars picked up something like 30 odd horsepower with headers, but up around 5000/5200. So if you had 3.23 gears with a TF auto, you might not get to 5000 in Second gear, until 77mph ..
But if a 4speed and 3.91s, then 5000 in Second is 53mph, now the cam wants headers, cuz 77 will be top of Third gear and flying!.
