Did the guy lie to me about the car?

I blew up my last car and traded it in for a 3000gt sl and payed 500 bux at the dealer. SWEET DEAL. Well the odometer shows 191,000 miles. He said the motor was swapped and really has 115,000-130,000 miles he not sure but some where around there no paper work to prove it. But ya I own the car now. No leaks from the under carriage, drives perfect shifts smoothly, oil pressure is great, gages show good things, battery is great. How do I know he's lieing or not about the miles? I think 191,000 pretty high miles for a car with no problems or I could be wrong.. ?