On a side note '92/early 93 magnum ex manifolds have a ~2 & 5/16" outlet as opposed to a 1&5/8" outlet on the later ones. A guy on FABO is selling ported out manis & you might peruse his post to see what info can be gleaned from it. (might be under "mechanical parts for sale"). I was thinking that a 68-70 340 pass ex mani flows the best (for the pass side) but are rare & very pricey but if I read his thread correctly he is sayin the large mag one does or maybe he is referring to his ported ones (I need to get back over there myself).