I'm thinking your heads have been cut and the intake wasn't. Did you use a front and rear seal on the block. You might try and set the intake on the engine without end gaskets and see what it looks like.
These heads have been in the family since 1975 and they were on the original 340 ( and still are ) they came on. To my knowledge they have never been cut.
I did not use the end gaskets, I used rtv on the ends.