If you're talking durability, /6 hands down. I know in my younger years I did my share of trying to blow em up and never did. I broke everything else in the drivetrain though. :D
I'm with Bad Sport ... they're not powerful or sexy, but the 225 Slant-6 "Leaning Tower of Power" was uber-reliable and dependable. My Dad got hundreds-of-thousands of miles out of them. His Darts, and later Dusters, would literally turn into rusted out "Flintstone-mobiles" around him. When he could no longer fix the body, he would find a new "donor" body for him to transplant his Slant-6 into. That "Leaning Tower of Power" was virtually indestructable!
Funny side note. In '88 or '89 my folks were shopping for a new car and they stopped by the Dodge Dealer as my Mom liked the look of the Dynasty. As they're working on making a deal my Dad tells the salesman that he wants the Dynasty but with the Slant-6 because "it's the best engine ever made." The salesman looks at him and tells him the Slant-6 hasn't been made since '78. Shocked, my Dad tells him "deals off! Lets get out of here and find ourselves a nice used Duster!"
