If your in brissy have a chat to Greens Nice, Kevy Brown.
IMO 250 @ .050 is still perfectly streetable, my new cam is 263 @ .050" and I intend to street it when the engine is finally back from the machine shop. So reconsider your cam choices.
Give us a budget and we will throw ideas from there, but what i'd look at would be something like blue block, crank, rods, Dont think you can get ACL flat tops anymore so probably looking at SRP forged slugs to get a flat top piston with thin rings, think its the only thing off the shelf. Get someone like kev to look over the 12 port, a basic 180 CFM job souldnt cost you to much. Either webbers or 2" SU's if you must go triples but a 500 holley spun 90 degrees on the blue motor intake manifold ala oj style would work, according to oj atleast. 240-250 on the cam. Stick with 1 1/2" pipes, so HM HM9's, not the C, or probably better pacemakers as there 6-2-1 and shoudl give you a bit more torque....
Million and five ways to go though.