Just a guess, but I'd think they're probably good for just over 120 mph which is moving pretty well....I'd say that's around 400 awhp....How fast are you looking to go?
We made over 500 rwhp with the stock feed line and a -6 return line. The reason for the bigger return line was we ran twin walboro 340's full time, didn't want to mess with the hobs switch and related wiring.
he breaks all the rules and gets away with it !!!