My Charger had a 75-ish low comp 440 with 1 7/8" headers, 3" mandrel exhaust, elect. ign. (with a REAL curve in the distributor, and that is a BIG deal), and it had a Holley 750 vac. secondary with a custom fitted K&N stub stack. I had that thing perfectly tuned/jetted and it ran very well for what it was, and then i added a Holley Street Dominator intake (highly recommend!) and suddenly i had to jet up to 80, from a happy 72 (which i believe was jetted up from the stock high-60's?).

The Stub Stack 'adds' CFM, or at least the effect, so my 100K + mile low comp New Yorker 440 actually wanted MORE carb than a 750. No head work, no cam (stock non-HP cam... ugh), no compression. Dont go with anything under a 750 carb. Tune that engine.