A gen I with original tires would be SCARY. The tires were knife edged when new (practically zero progressivity), and age would worsen them. I say get rid of the hardened tires as soon as possible.
Regarding the plugs there are driving behaviors that would be detrimental. If the car was only moved from here to there and seldom driven to the point of warming the engine fully. I would be concerned about fouled plugs, in addition to many other things like oil quality, exhaust system corrosion, etc. 200 to 300 miles per year cannot be good for a car. I would also bet that with that mileage the owner did not provide enough service. Many servicing aspects have time limits in addition to mileage limits. Things like coolant, engine oil (every 6 months if you drive it or not), transmission and differential lube, brake and clutch fluid, etc.