273 intake vs. Edelbrock 1406 carb

I'll chime in just because, like you I lurked this site a long time.. and you're dying over there. That said, I'm nothing compared to the brains on here :)
It sounds to me the base of the carb isn't square. And it's probably a dumb question, but have you checked the sqaureness of it with a straight edge? Metal ruler or something? Manifold too?
Did another carb seat ok?
How do you know it's leaking on the pass side?