I agree that w/o logbooks it is best to leave it.
The mismatched engine hours, and mismatched prop hours, may indicate a prop strike or similar. Certainly you must get a really good explanation for that bit.
But loads and loads of old planes have missing logbooks, and not everybody has the budget to buy new or newish planes. The vast majority of aircraft owners are not pro-active maintenance "micro managers" and they just dump the old heap at some MO and (usually) write a cheque at the end. Then the company goes bust. I have owned a plane only since 2002 and already have seen CSE (shock load inspection), Air Touring (loads of maintenance and extra work too), and a few other people (including a firm which did all my maintenance for 2 years after the 2 year warranty expired) go bust. Luckily, because I know the ropes to a reasonable degree, I got the paperwork from them before they went.
And nowadays I photograph the Annual work pack every year.
So far only one company has refused to send me a work pack for an overhaul job. I reported them to the CAA but they are not really interested. So I have to get the item overhauled again, this time in the USA.
So it's easy to lose maintenance records. I don't believe a CAMO would refuse to take the plane on board, but they would spend extra time on it checking stuff. A lot of ADs can be verified by inspection. Some, and also the replacement of (non serially numbered) lifed items, cannot be, and I suppose there is a lot of potential for getting screwed. Especially by a less than honest MO... One solution would be to continue to use the existing MO since they are "obviously" happy with it
As regards this particular plane, I hope the buyer knows what he is doing because he is basically buying an old dog. It might be a good old dog, or it could be a really knackered old dog.
Starting with the avionics, if any of it doesn't work, you need to think of 4 digits plus to fix
that item. So make sure you (or somebody else) understand it all and check it all in flight. Especially the autopilot
There is some truly Imperial War Museum-grade stuff in that panel.
The airframe needs a thorough inspection by somebody familiar with the type.
I get asked a lot by prospective Socata TB buyers, about various for-sale aircraft. I know one very good man for a pre-buy check but I don't know if he is a Piper specialist.