I agree with the rings sentiment.

It may be difficult to verify it 100%

I had a 360, that had no leakdown, and good comp on all the holes. The comp was so good, it only smoked a little under load (the oil was all burnt) Upon teardown, I found the oil rings were gummed up. The comp rings were still good, which is why the tests were useless.

In any case, if the motor is as low miles as stated, just buy a rering kit(rings, bearings gaskets, seals) and tear it down at home. You can likely do the whole thing for well under 1K if you do it yourself, and don't need to machine anything. Even if you get a head shop to do a basic rebuild on the heads, and you do a scratch hone to the cylinders so the new rings will seat.

I've done it many times myself with good results, BUT you always have to be prepared for the worst. Hopefully you don't tear it down, and find a basket case.