This is a long shot. But when I was looking for the intake for my 283 I took notice that some older manifolds needed a bit of grinding to clear an HEI and some it just wasn't going to work. Of course I can't name which ones. Anyway, any chance they were grinding for clearance and went a bit deep. (and made a vacuum leak in a hard to see spot) Like I said, a long shot but I thought I'd toss it out there.
Pete Geurds Douglassville, PA
