I can't answer your question but I have a silvertop with Kent sport cams (stage 1) and was considering an upgrade to stage 2 (Kent super sport). I know you can't fit stage 3 to a silvertop unless your change over from hydraulic to solid lifters. Stage 1 are 262 duration, 42 overlap 10.4/9.5mm lift (21/61 61/21). Stage 2 is 278 duration, 62 overlap 11/11 lift (31/67 67/31).

So, if you have stage 2 and they are ok for hydraulic lifters we could consider a swap. Anyway, hope the info helps.

John