X-heads enough for 408 stroker?

I don't have the specs offhand yet the 1970 340 I removed from my Signet couple years back ran the 1970 U heads which are the same as X heads and it was dyno-ed at 479 horse power. It also ran any gas from 92 octane up without a problem till others f***ed with the carb, timing and valve adjustments. I sold the heads for 900.