Dorman's a solid, reliable brand. Haven't looked at their slant-6 exhaust manifold in quite awhile, but last one I saw was good. I also haven't closely examined the ones from 1aauto.com (and on ebay from that same seller) but those over on slantsix.org who have used them have found them quite acceptable -- though they've required some grinding of casting flash off the outside of the runners to make for easy access to the attaching hardware.