1970 Nova Worth $7500 or not?

I know a guy selling a 1970 Nova that has 42,219 miles on it. It has minor rust on some parts and two major rust spots. It has the origional hubcaps and had a 307 but blew so now it has a 350 bored 40 over. It had a 4 speed transmission. Miles on the motor is unknown but they claim to have only 7k on it. It has minor transmission and minor exaust leak. It starts right up abdithas a clean title. Interior is perfect only has a cracked dash but theblack leather seatshave no cracks just a little dirty. He says 7,500 and I can have it. Now im not much of a classic guy but I was told if classics are not all origional than they are not really that valuable. Also my uncle says a petson could disconnect themileage guage and drive the car and it will not read the miles. Anyway is this car really worth $7500 because I have seen others in about the same condition for about $2500. So am I getting screwed? What you pay at most for it?