Almost all of my heads exhaust studs needed to be helicoiled. And I think that was from a warped cast iron manifold. Well I thought I had a deal on the Thorley header but the price on line changed. I have to wait and see. Are Trail Gear headers any good? Prices are not so bad and a nice thick flange.
Make sure the brace between the exhaust and bell housing is intact. Eliminating that brace will eventually damage the threads in the head. When I installed my header I made a custom brace due to the factory one no longer being compatible. I also like to use a flex pipe to be safe.