the isky 1012b was the '64 s/s wedge race cam; 320 degrees duration, .520 lift, 108lsa, a lot of cam. the 1012b was superseded by the racer brown stx series; stx21, 22, & 23. the ssh25 and 284-.484 are identical for all practical purposes. the real issue may be how much head modifications your willing to do to run a high lift cam. there are 114lsa versions of the 284-.484 and 292-.509. in my opinion, none of the above.