Electronic ignition upgrade
If you cant find a 400 dizzy, though i dont know why you wouldent be able to, mopar made a kit that allowed the use of an RB 440 426 dizzy fit the B 383 400 block. It consisted of a spacer, and a longer clamp with bolt, but if you can find a B engine dizzy your better off. Mancini racing has remade that out of production adaptor kit.