The GM 5.3 is all I know about from experience. It does fine (depending) but, likes the RPMs. That took some getting use to. Mine is a daily driver so, I don't really want the bigger engine. I'd totally buy another Chevy/GMC with the 5.3 for towing what we tow. I do think the extra horsepower would be nice to have, especially on the mountains. I'm in 2nd gear at 50-55MPH pulling mountains. The RPMs are somewhere between 3500 and 4000. It no longer bothers me. I was use to a 454 and so, there was an adjustment period. For feeding to drive every day I'll take the 5.3 over the 6.0/6.2 every day. Keep in mind that our RV is 5765-ish dry, under 7000 wet.