I have only a single carb on mine (S&S 2-1/8") but I moved my radiator fill tank. The new position is just slightly higher, which works fine.
This is a really crappy picture (because I wasn't trying to show the fill tank). The right side of the picture is the front of the car. Towards the left side of the car, you see a circular device (it's the fuel pressure regulator). Directly to the left of that is the fill tank, mounted on the slanted area about the passenger footwell. You can see some of the brass color as the black paint has worn off. I remounted it here so I'd have more room to duct cold air to the carb.
As you can probably guess, the real reason for this picture is to illustrate a last-minute, hack-job repair I did on the car when a carb stud stripped during race practice. I clamped the front part of the carb on with vise-grips (and safety wired the vise-grips in place). Got second place in a one-hour enduro at BeaveRun with this setup!