I had that in my 164 at 204,000 miles and thinking it was rod problems put
in a different engine. When I finally tore it down and plastigaged and
miked it I found the following:
Zero measurable wear on rod bearings
Zero measurable wear on main bearings
less than 0.005" wear on the worst cylinder
Could have used a valve job
Bad fiber timing gear.

I suggest you try a timing gear. Lot cheaper than an engine change.
--
George Downs Bartlesville, Heart of the USA!