Do a complete inventory, by make, model and serial number of every component installed. check equipment list for reflection of that equipment.
Then run a AD list on every installed piece of equipment and verify that every AD has been complied with, on each appliance, not just signed off.
When you know the aircraft is legal, go fly it, see if each Appliance works. check engine oil pressure when hot, to insure it doesn't fall below mins.
Next check the engine aircraft and prop times, and if they were in fact signed off properly at last overhaul.
Check with the FAA data base for the legal owner, and find any liens against it.
Make sure you see a data tag on the airframe and one on the engine and match it to the log books. No data tags 15 cents a pound for scrap.