I've got a sbc 327 of a mid-sixties vintage and it has the road draft hole in the back of the block topside. But it also has a threaded hole next to it also in the block. The threaded one is the one I'm asking about. I see where the distr. goes into the intake and the distr. clamp bolt, also on the intake. I'm curious what it goes to and it seems to be a few inches deep if that helps.