It's not the chassis that is the issue with the 340 driver's side manifold, it's the fact that the EQ and MP R/T heads don't have enough meat around the exhaust port at the bottom for the manifold to seal to the head. That manifold works fine, if you use an OEM head, but if you want the better heads (like an EQ), you run into problems getting them to seal.
I'd link you to pictures, but lunch is almost over. You could search on my user name and you should be able to find more posts I have made about it.