I would run a leak down test first. High compression could be a sign of excess
oil on the cylinder walls. It's not uncommon to see
oil scraper rings installed incorrectly. If everything on the lower end checks then I would look at the valve seals and the type. You can check for excessive guide wear without pulling the heads.
If your still looking for a top of the line machine shop with real world prices go see Bobby Gaines at Bell and Gaines in Modesto. I've been using him longer than I can remember.
I do have a leak down tester you could borrow.