My experience with the slant 6 were far from bulletproof, last one I had was in an '84 1/2 ton Dodge, which I bought new. It broke two exhaust manifolds due to overheating trying to maintain 55 mph into a 50 mph head wind, yes twice. Also it came from factory without completed machine work on the end of the camshaft, starving the lifters of oil. The dealership put in 7 sets of lifters before it was tore down and found the cause. It also ate starters, they usually lasted 10,000 mi., also due to overheating/ not adequate heat shield to protect it from exhaust manifold.