Gold, The outer diameter is definitely a countersink that leads Down into the hole. The second picture, left side Is my best shot of the c'sink. Is this an issue? If so, can I use a soft washers help Seal it? The second picture makes it appear that I can see down past the hex of the plug. This might just be a optical allusion.
1970 YO7 A66 [Canadian Export] F8 Challenger 340 (Currently in shop for stroker assy.)