It really would not have taken much for the factory to bolt em on, surely they could have been made to pass emission regs of the day? Same with the magnum R/T head, actually they would have been even easier as there is nothing else needs to be different to put em on and surely with the much improved injector targeting MPG and emissions are improved (they no longer squirt into the side of the port)... I suspect they didn't use the magnum R/T in production because they were big inning the new hemi development and wanted as drastic of an improvement over the magnum as possible when they introduced them.