The bike at the very top has the same TPrince 92 mmtop ends as I used, could even be from the same batch. That bike must have a stock 90 mm stroke to get 1200cc whereas I used a 102 mm crank to get 1360 cc.
I see they are quoting 115 HP on the 1200 version with HC pistons, doesn't say which cam. I think to get that kind of HP from a 1200 it would have to be Terry's MK 5 cams, which give the greatest power from a Vincent.
I'm using the HC pistons on the street along with the MK5s, no problem so far, just a beast to kick over at 10.8 to one and 1360 cc.
Of interest, Horner's used Terry's top ends on their first Vincent racer. I doubt if they have moved far from that design, it is a very efficient head, a copy of the late model Norton Manx head further improved by Steve Hamel's input using modified Prince heads to get 120 RWHP from his 998 Vincent Bonneville racer.
Glen