For 200bhp I wouldn't even bother with an ST170 bottom end.
RST manifold with adapter or tap the head, I think a standard RST T3 will do 200, decompression plate, even the standard plastic 2.0 Focus inlet would suffice.

200bhp on a Zetec wouldn't be cheap, will require headwork, AT LEAST ARP rod bolts, ITB's, Megasquirt and a decent 4-1 IMO.

Personally, 2.0 Silvertop on something like Gixxer 1000 carbs, Megajolt, 4-2-1, could skim the head for a touch more compression and I'd like to see 150-160bhp, cheapish too.