Can you just mark the bottom of the hood around the air cleaner, then take it off, flip it over, heat and hammer the clearance into it? All the rules make it sound like OEM Gold judging at The Mopar Nationals instead of beat n bang racing.....lol.
If the adapter you already have is one of the stacked type, with 4 bbl on one side and 2 bbl on the other, making one at one level may help.
Do they have rules about gutting the bracing from the bottom side of the hood? Might be a tad bit of room there too if they don't care.
One other thing you might be able to do is to make a carb adapter out of a single level 1/4" piece of aluminum. Cut it out to fit the intake with a thin gasket and bolts at the 4 corners, then center the 2 bbl gasket up and drill the mount holes for the 2 bbl carb. Flip it over and countersink...
Back in the day, (which doesn't do you much good now) there were many, many 8 3/4 gear ratios produced for Mopar circle track racers. Dave Marcis used to live right down the road from me and his race shop wasn't far away. Sometime in the 80's or 90's he had an auction and sold off all of his old...