I was just looking at this thread and wanted to add the photo of a 68 273.It is without a bolt with a hole or a drip tab.It did have the crank oil slinger. Behind the thrust plate there were no plugs the oil galleys are open using the thrust plate to seal them off.I have heard of drilling the plate with a small hole to squirt oil on the chain. Has anyone done this? If it was mentioned above I may have missed it. Great thread !