go for gt17 saab turbo and fusion fabrication manifold that's what i have and no need to cut bulkhead. only part hard to find seem to be turbo carbs with locking ring around dashpot. if you get a full tubo engine then can keep your n/a one as spare and probably save money in long run.
Are Fusion still on facebook? The diy flanges & bits seem to have disappeared from fleabay.