magnum matched to 904

all pre magnum converters and flex plates are off set mounting holes,,period,, it has nothing to do with internal or external balance,its just the way it was,,
i have not delt with a modern,magnum set up yet,,,,but im sure mp has a balanced flex plate to make your old style 904 and converter match up,, if not B&M has flex plates,, try jegs or sumit,,i doubt a local trans shop has any clue as to what your doing,,,