most generic shelf cams use lobes desighned for the smallest common lifter, the chevy, so even ford and chrysler with their larger lifters typically get stuck with the smaller lobes because it is easier to just make one small lobe and use it on everything than 3 specific lobes. Also just because a ferd, chuby, mopar use similar part numbers from a common manufacturer does not mean they were made the same, differnet head flow considerations and displacements require different lobes for optimal performance. Also ferds usually use higher rocker ratios so even if they do use the same lobe they will have more lift.