depends on the purpose of the truck. my friends dad took an older dualie, built up a monster engine with a full time blower, lowered the suspension and put street slicks on the back instead of the dual tires. that sucker would roast most things he came across. id say the purpose of that truck was all speed, and having it sitting up higher would be a detriment to its purpose. its purpose up to that point had been "rust creator", so i think it was a good decision.
my truck is all stock, but looks lowered since i need new shocks. i do think the guy i got it from had leveled it out tho, it sits dead straight. i like it. havent seen a decline in usefulness tho, i can still carry 1200 or so pounds (electrical gear) in it without much trouble. engine is getting tired tho, working on refreshing that part now.