We have owned several Chevy 6.2's, four Cummins 5.9's, and even a Ford 7.3. The 7.3 and 6.2's were naturally aspirated and really lagged in pulling power. We owned the 7.3 from new till it had about 50,000 miles. The 7.3 never gave any troubles, but it really liked fuel - just driving around it probably got about 12 MPG and pulling a trailer it got about 8. The 6.2's (4 that I can remember) combined for almost a million miles with the highest being 400,000. They were really good and reliable engines, but couldn't pull the hat off your head. The 6.2's got really good milage on the highway at about 20. We have owned 4 (one is brand new) Dodge trucks with the 5.9. The three (04, 91, 92) experienced 5.9's have 230,000, 200,000, and 210,000 miles respectively. The 91 and 92 pulled stock trailers for about 150,000 each and have never had any problems with the engines. The trans and diffs in the 91 and 92 are junk. The '04 has 230,000 miles and 229,500 of the miles are pulling a 28' livestock trailer. Half of the miles are empty (13,500lbs) and half are loaded (24,000-29,000). The '04 is absolutely the toughest and best pulling truck we have ever owned. We have not had to spend a single penny on repairs for the engine, trans, or diff - I'm really really impressed. Engine oil is changed every 15,000, diff and trans are drained every 60,000. I can't even begin to describe the pulling power of the '04 5.9 HO - out pulls everything else we've ever owned by a mile - no contest.
Wayne