Priobe,
You have tried or answered any of the things I would suggest. I do see you are running a 20w/50w
oil and its readings were hot and cold as you mentioned. You asked me about (external bypass possibilities I refered to.
Oil filters manufactured for GM, Chrysler and others have an internal bypass disc built into the filter (this bypasses the filter element) but the #8A does not have this and is in the housing. Some remote mount base mounts have a pressure operated bypass built into them and this is more common with a non-bypass type filter application like the 8A used on Fords. I have seen the in/out reversed on a remote filter mount causing the engines bypass to open.