I had a very similar problem with carb clearance on my frame, I found simply cutting the intake manifold would allow me to rotate it - changing the angle and canting it to the side. You need be careful however as if it's an aluminum intake, it's nearly a 1/4 inch thick sidewall and if the two halves aren't flush it will interrupt the flow and collect fuel. If it's a steel one, the step is so marginal it really doesn't matter much.
Another concern to be wary of is vibration, should you choose to extend the manifold - be careful to mount it (carb) securely to keep the shaking down, frothed fuel is not going to help performance lol
*My carburetor is more level than it appears in this pic - my camera was held by a slightly crooked person heh