I hate to be a nah-sayer but you really can't say the engines never been worked on or make a statement like that unless you are the original owner and the car has been in your possession since new. Like I bought mine when it was 10 years off the showroom floor and I always used to say the Trans and rear end were original. But years later I blew a couple gears and had to repair the tranny. Turns out it was a 64-67 case. Apparently it had been replaced sometime before I bought it. Lesson learned. Tough to prove absolute statements like that.
Just sayin...