I tapped the head for threaded inserts and then used stainless 3/8 threaded rod and locking flanged nuts (cheaper than stock 10mm)
Also make sure your manifold is warped, I had to resurface mine.
(It's possible to drill and tap the head in the engine bay......)
Although this may be a perfect solution, some exhaust header manufacturers do NOT recommend using stainless steel studs or nuts.
Gnarls.
