I'm looking at a 1977 6.9. The car is being sold by a local dealer for a charity, it has 152k but there are no service records. The car is very clean but there is some rust under the rocker panels. I owned a 1976 450sel for ten years until it was wrecked it ran like a clock. How would the 6.9 differ in regards to maint. and service? would it be as reliable? I am going to have a mechanic check it out before I make any moves but I would like some feedback from someone who knows about these cars. Any major problems to look for? Thanks.