Well, I wouldn't exactly call it an "upgrade" to mount 26mm torsion bars. You can crank stock bars just the same as larger bars. The larger bars are not stronger and they don't provide any additional lift bythemselves. All they do is make the ride the stiffer. It's like adding more springs to a leaf spring pack.

If you have an excessive amount of weight up front, like say a 15000lb winch, solid steel bumper and about 3 batteries, then it might justified to have 26mm bars. Or maybe if you transplanted a Cummings diesel. <img src="/forums/images/graemlins/smile.gif" alt="" />

At most, I wouldn't go more than about 25mm bars, which sway-a-away at least used to make, but for most, stock bars should work just fine. In other words, if that's a parts truck, those torsion bars are not parts I'd swap over to your real rig.