So I went for the center hole today. Did it in 3 steps. Used a light after first pilot went through. This took a lot of time. The deck is thick, probably just under 1/2" in this area. used a new drill bit on the other side. Used a tiny bit of cutting oil.
Max hole was .265 due to proximity to the head bolt boss. That said, maybe could have moved it up, but wouldn't have been centered in the gasket hole.
I am happy with this. Will work just fine. so here are some pics. Some you may never have seen ( inside)
