do a search for PartsCo , new zealand mob i believe, they carry a good extractor option for N/A Skylines, You'll also need to purchase the Exaust Manifold gasket, (~$90 i believe).
1989-98 Nissan Skyline R32, R33 - RB20, RB25 DOHC. 1 1/2" Primary 1 3/4" Secondary 2" Outlet Part #D12
That should do the trick Im also doing the extractors at the moment, im pretty sure im gonna go with the Coby's, unless someone can advise me otherwise.