Tim,
You might want to post a photo of that plug/hole, to make sure we know what is being referred to.
If the plug almost fills the oil line opening, a full-flow filter has never been installed. That plug is supposed to be pushed aside when the full flow filter is used. After the plug has been moved aside, it is imperative that a full-flow filter be used, or
a jumper line should be placed between the two oil filter ports on the block.
I do not know if a bypass filter can safely/effectively be used when the plug is visible (has not yet been moved aside).
Wait to hear from others for a confirmation or correction.
