A factory Slant 6 with a 8 1/4 differential

yeah. maybe an h.d. option package or something. maybe a package that included bigger rear end and front sway bar. i wonder if anyone has a 74 dealer brochure. maybe that would answer this for us. and who knows. maybe it was standard with disc brakes on the dodge darts, but not on the plymouths? ok now im just guessing but that seems like something that could have been.