I'm just thinking out loud here, asking the sixpack intake too feed 440ci has worked well in the past, but does it have enough air flow too feed 540 cubes? seems too me the runners would be pretty small. I know there was complaint years ago about core shift with the molds.

Question 2, the slight stumble before the outboards pop open could this be reversion in the intake? The engine wants too pull but its sucking threw a straw as the rev's build the outboards kick in and the air velocity looses momentum before it picks back up again? So with that thought it seems too want air would a larger center carb get it over the hump before the outboards kicked in or would this just move the stumble higher up in the rpm range?

#3 The jetting seems pretty close too the bone at 540ci, I would think it would like some more meat too eat on.