I have an old '76 F-250 with the 300 straight six in it. I don't think that thing will ever die. Ford's 300's are almost as legendary as Toyota's 6 where I'm from. It has a main bearing between every piston, very simple, sturdy design that just doesn't stop. It get's better gas mileage than my 80 too!
I've gotten 21-22 mpg on the highway reliably with it.
