Sorry to dig this up, but wondering about anyone using these headers with EQ Magnum and/or MP R/T heads, not just the standard ones.
An OEM head has more material around the bottom of the port and allows for the big port LA headers/manifolds to seal. The EQ and MP R/T head doesn't have the same casting and the heads stop just below the port leaving little to no material to seal the large port LA headers/manifolds.
The exhaust port are different. They match closely to the LA 318 ports, but are significantly shorter than the LA 360/340 exhaust port. And with the R/T and EQ heads, they don't seal. Picture here -
5.9magnum questions
More discussion -
Are the TTI shorties really my only option?
Here's some pictures of a Magnum head with headers and the leaks it had -
10 Day Magnum Swap - '65 Dart 270