GM has offered several series of alternators over the years, each time taking a step up in performance. The great thing about these alternators and aftermarket brackets is that for the most part they are interchangeable. Starting with the externally regulated 10dn alternator of the 1960s and moving all the way to the CS130D alternator of late, aftermarket brackets with rod end tensioners will interchange. The 2" mounting foot width is common to all of them and the 6.61" bolt spacing is common (except the CS130D has 7.24" bolt spacing, which many brackets accommodate). Race Prepped Alternators feature a balanced rotor for high rpm applications.