You can use your current 904 convertor, if it is neutral balanced- if it's not, remove the balance weights.
You just need the correct flexplate, such as this one from Bouchillon:
Flex Plate (A727 / A904, Hemi Gen3) - Bouchillon Performance Engineering
If it needs to be SFI certified for racing, ATI has this:
ATI 915685 SFI Approved Flexplate 99998305761 | eBay
