I'm running a 572 Hemi, 880 HP / 770 TQ, dual 800 carbs, idles from a dead cold after 30 secs, 280 @ .050 roller, 15:1 idle, cruises in the high 14s, WOT mid 12s.
Their 550hp is from about 380ci. The Barton motor has a big cam, single-plane intake, and very poor vacuum signal, so it always ran somewhat rich at cruise. (Otherwise, it would lean out.)