Just passing on a little information. A long time ago, maybe 15 to 20 years ago, I saw a Stage II (153) on-center block that had been reconfigured for internal oiling. The pump cover appeared stock with everything inside. This guy, I think they called him the "Professor", had created internal oil passages so it worked like a stock block and looked like one too! I believe he did a handful or so in various forms and I think he also converted some 109 stock blocks to 14 bolt heads. He must be dirt old by now, seriously doubt he could duplicate one of those again. So, for your information, I know for a fact that it can be done.