The Demond carbs I've worked on had issues of not
responding to the idle mixture... I have a 850 holley
DP on my 416 and it loves it. quick response and
makes just under 600hp on the dyno... I think you
would be better off with what you have.. it'll need
some minor work to lean it out... if you dont like
playing with them or dont know how, take it to a chassis
dyno