302 Swirl port heads vs 340 X heads

So I have a set of 302 Swirl port heads currently on a 318 that I am building as a seat time race engine. Hope to run 13's high 12's in our Dart. I just found a set of 340 X Heads that are available. Would they benefit us on 318 for some extra HP? If so what is a fair price to pay for them?