The /6 head is the greatest weakness when it comes to power, a fully built na /6 power limit seems around 300 hp. Most warmed over /6 probably lucky to make 200hp.
It's not luck, and any decent attempt at making power will be about that, a serious plan for a really hot one will easily exceed that. Mine fell just short of 200, and it was under-carb'd, at 196hp. :thumbsup: