•Engine was overhauled a year ago & is still being run on straight oil
That well may be part of the problem.
Lets review, engine overhauled one year ago, and still using non-AD oil.
Not an especially good idea.
So, I would do the following...
Change oil (use Phillips 25W50, is my recommendation), remove and cut open/inspect filter, install new filter, and test run.
Oil light should remain out.
I absolutely would not fly with the present scenario...unless someone was chasing me with a big gun...