[David E. Clark]

Those numbers are fine. From my experience, the most important factor you are looking for in a compression test is consistency between cylinders. There should be no more than 10% variance between cylinders. In your case, assuming the test was done properly, your low cylinder is 165 psi and your high cylinder is 170 psi. Roughly 3% variance which is excellent by any standard! If you are really worried you might request that your mechanic (or the seller) do a leak-down test. This test measures how much "pressure" (PSI) is lost in the engine while the compression test measures how much "pressure" (PSI) the engine can produce. It is generally accepted that the leak-down test is more indicative of engine health than the compression test.

I agree with the advice of the other members that you watch the seller perform these tests; or, even better, learn to do them yourself - it's not hard! Not necessarily because you think the seller is a crook but because with these old cars it's always helpful to learn as much as possible. Good luck.