First off have you described what you plan to use the truck for? I breezed through the posts but didn't catch your intended use. Will you be towing seldomly, often, or even at all? Daily driven truck or only driven when truck is being needed?
From you saying you run your 2wd v6 to death, and the $$$ you say you're prepared to spend, my vote would be on a newer body style GM 1/2 ton (chevy or GMC) 07+. Those 5.3's are stought for a half ton v8 and I've heard the resale value be mentioned about a Tundra, I don't think a Tundra would hold resale value better than the newer GM half tons personally. There's way more GM half tons on the road than Tundras meaning more people seek after that truck. Best all around truck in my opinion if you don't need to do alot of heavy hauling. My friend has a 07 new body style ext cab Z71 and used to pull his lifted Cherokee on 38's on a 16ft trailer with no trailer brakes back and forth to the trail all the time before he sold the jeep. Pulled and stopped it fine. If I ever sell my 2006 GMC 2500HD 6.0L gasser, I'll most likely be in the market for an 07+ GM Z71. Just my $0.02.
....but if you plan on hauling heavy **** alot, then an 06+ D-max would probably be better suited.
. . . . Just something to think about . . His is a 1/2 ton 4wd with the new 5.0 and the automatic 6spd tranny
