[Rich69shortfleet]

Well sure, it's a pickup so of course it flexes some. Tying the cab and the box together would do more to eliminate flex. But there is little you can do to the frame alone without adding a BUNCH of weight and complexity that would greatly reduce flex. Are you planning to run your truck on a road course?

In addition the frame is freakin' HEAVY (I mean, it's a truck so it should be). The suspension is heavy, huge amounts of unsprung weight, and a solid axle. The best way to carve corners in one of these would be to make a tube frame chassis and wrap the truck sheetmetal around it. They are also tall with a high center of gravity. Even with a lowered truck, the engine still sits a mile above the frame. Not to mention the obvious forward weight bias found in any pickup.