You need the factory stock flex plate for the 98 5.9 Magnum, and then run a neutral balance converter of your choice...be it for a 727 or a 904. 5.9 Magnums are balanced on the flex plate, not the converter like our old LA 360's. You will have to rat one converter bolt hole out on the flex plate to get the older converter to bolt up. It takes very little filing to make it fit. Mark the flex plate and converter with a dab of paint or something so it's easier to line them up later. Hope this helps.
