I have a 1966 MGB with the original engine. It did not come with carbs, but it did come with two intake manifolds. Both of these are the later style that use the sealed EGR valve, but I would like to use the original style with the removable cap. The original style mounts on a straight nipple, instead of one that is parallel to the ground. How are these nipples mounted in the manifolds? Can they be removed and replaced? It looks like the early ones were threaded in, but the newer ones look different.