a lot of the heads i have seem the very first one and very last one are alignment studs with no threads on ends. they just sick out enough to aid in instillation of manifolds. they can usually, and it is recommended by several knowledgable folks, be removed with a pair of vice grips and regular ones with fine threads on the outter end can be installed. the problem i have had is if manifolds work loose then they warp with heating and cooling cycles. then it will take resurfacing the 2 together to get them to not leak.