10 Day Magnum Swap - '65 Dart 270

DionR said
Based on the picture shown on Jeg's website, I would say you will have the same issue. JEGS EngineQuest Mopar Magnum Cylinder Heads | JEGS High Performance

I don't think the cast iron HP manifolds have a different exhaust opening than a standard low performance manifold, so I would guess that any A-Body exhaust manifold used on an R/T, EQ or similar head would have this issue. I know there are two LA exhaust gaskets, the pressed metal one and the fiber one, but I don't know if the opening is different between the two. Regardless, I am pretty certain that no matter what manifold is used, if the fiber gasket is used with it, there will be a leak at some point in time.

The magnum gaskets are exactly the same as the 318/360 ports with the EXCEPTION of 340 HP. I have downloaded a photo of the 318 drivers side from my 67 GT Vert we just yarded for 5.9 magnum swap. We sell 4-5 pairs of EQ's a week and use them on almost all our cars and they are the same as magnum head with gasket match. we also beat Jegs on price and quality.

318 exhaust.jpg