Roots style on 400

ATI 917110E: Super Damper Chrysler 361-440 | JEGS

For an internally balanced Roots blown BB Mopar I’d suggest this ATI Damper.
It’s double keyed, has six 3/8X24 (stock is 3/8X16) pulley threads and spaces the pulleys 3/4” further away than stock. It’s made in the USA too.