Maybe I'm influenced by the huge hp numbers thrown around here, but it doesn't seem like you need to be all that careful when trying to get 200 whp out of an L28.
I would think that you could get very close if not reach your 200 whp goal by installing an N42 and going with a larger cam (something in the .500/300 range). You'll need to do some modifications to run a cam that big, like installing aftermarket springs and retainers and shorter valve stem seals, but the bigger cam would be worth the effort.
If that didn't quite get you there, triples certainly would. My opinion on triples is forget about the 40s, and go with the 44's or 45's. I think you'll be really close to your goal without them though. Ported SU's are another option, but I think the triples will ultimately make more power although they're harder to tune.