I wrote about this several months ago, and I found very little interest in it. I am glad someone out there cares.
he 5.2 and 5.9 Magnum manifolds from full sized trucks look like winners, but only the right side fits. It is actually a really good flowing piece, and it has a superior design feature: the outlet flange is just above the oil filter, allowing for a much less restrictive downpipe. I have no idea why Chrysler installed center dump manifolds in these cars. The downpipe had to snake around the chassis AND the idler arm. Each bend in the exhaust adds backpressure. The Magnum RH manifold allows the downpipe to have ONE 45 degree bend.
The left manifold is the tough one, as I am sure you are aware. The best fitting and flowing manifold is the 68-71 340 piece, followed by the 72-73 340, then the 74 and later 360 manifolds. A Jeep Cherokee LH manifold might fit. The Durango and Dakota models also had the 5.2 and 5.9 magnum engines, and they may fit. I'm not sure.
I had a 70 340 manifold on the left and a 5.9 Mag RH manifold on my Frankenduster 360. They fit well. Good luck.