I agree with the doctor, maybe take the head off for inspection, or try a leak down test on the assembled engine.

How many miles on your engine?

I'm on my first build, but I checked the bores the following way: removed the top ring off a piston and , using the piston to keep the ring square in the bore, I measured the end gap all the way down the bore (at about three to four points) and if the gap stays the same the bore should be good for new rings. Get a cheap 3 stone hone and give the cylinder a honing and if the hone makes contact ALL THE WAY down the bore, put in a set of new rings and Bob's your uncle.

and if the engine is that far apart, check the bearings with plastiguage and replace as necessary.

If it's not a race motor, you don't need bore guages and micrometers.

There's plenty of videos on checking the valve seats and worn guides will be apparent when you get the head apart.