removing carb spacer

How about a scoop? Personally, I would try to avoid removing the spacer - a 1"wood spacer was worth 17 HP on my 340 and I've seen gains as high as 63 HP on big blocks. With a scoop being plan A, plan B would be finding a dropped air cleaner base that is clearanced for the Holley float bowls. Most of the ones I've had will give you about an inch of clearance by lowering the the air cleaner down over the carb.