i think the main reason no one TRIES to reach 200hp NA (unless competing in a specific class) is because for about the same money, you could put a turbo on it and call it a day. even mild boost will get you well over 200. no worries about which octane fuel to run, clearances or anything like that.
i think what you will spend trying to reach that on a naturally aspirated engine will run you well over what a turbo + installation and tune will cost.
It's been years but you could drop high compression pistons and new cams in for less than 2K and get 200+ RWHP on a Gen I. The bare min on adding a stage 1 turbo is around 6K, but typically gets you 30 to 40 more ponies.