I always tap and thread the ones I do, probably not neccesary, but part of the process anyway. I will have to look at the tap I have for the hole. I know I had to get another one that is longer for the one behind the dist hole. Only tip I can give is to make sure that the plug doesn't obstruct the
oil passage. Also since it is a pipe thread, it's tapered. If you want the plug down further, you tap the hole deeper, but remember what I said regarding blocking the
oil passage. There are also different depth plugs. Since it is tapered, as long as it's seated well it shouldn't leak, if the protrusion interferes with something you have the 2 above options.