I've been thinking about this issue for some time (started with fabbing a plenum to raise the 5200), and what I was trying to get around is trying to use a progressive carb. Even with the EFI intake, the only advantage is the longer runners on 2 & 3 (as it relates to a progressive). I'm looking for an EFI intake to modify for a carb specific combo. Using a 38/38, I'll mill the divider between 2 & 3 and 1 & 4 effectively making a dual plane intake. With the runners being closer to equal length it should flow fairly even between planes with the added bonus of being able to jet the planes separately. The only thing I won't know till I get in it is if there's enough low speed velocity to keep the intake charge from pulsing.