DrewP,
Looking at your picture, are there two gaskets below the carbs or is the one on the left the insulator? The gasket on the right looks like it would work for either carb. Are you using a gasket between the insulator and the manifold? I'm not sure if it calls for one there. But if you decide to use one there (I did on my YF), I would use one similar to the gasket on the right in your photo. The four slots should allow the air to move through. Having stated all of the above, I don't know jack about 261 intakes.
Carl
