Like it's been said before. Maintaning is the key. 89 350 crew 4X4 460... 242,000 Oil rings lined up. Did a FULL rebuild, at 258,000 miles the truck still drives like new. 84 250 4X4 460... 220,000 oil rings broke on two cyl. Econ. rebuild still standard bore, 379,000 Truck still does great. 80 350 460 truck has 500,000 plus. Motor is abused. Had 20 min. on rebuild and hooked to 37 ft. Travel trailer and flogged it for many hrs. The only time it runs it's geting it's guts pulled out. 140,000 still decent power but starting to smoke some. P.S. Infestation's suck. Kill em all.