The WS7 was a Novarossi based engine. Stock, they came with "standard" head, but a turbo head was an option. RB went out of business a while ago, so finding parts isn't easy... However, as far as plugs go, no need, as most standard plugs will fit. Like previously stated, a Novarossi standard "6" plug should be perfect, in colder weather (under 55* F) you might try a "5". There can be allot of other things that will effect your engine, but if you use a "6", it pretty much works all the time...