Boxed trailing arms, what is the purpose?

That would depend on how much the stock arms are twisting under acceleration.

Don't expect miracles.

I read it can quicken your 1/4 mile time by up to 0.1 second.

They give you better throttle response.

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Hey a 10th is a 10th. A handful of these small mods and you've got half a second.

M@ if you run adjustable upper control arms, is it the same thing as redrilling the mount?

Has anyone actually gotten under there and looked at the mounts on the body? Years ago I was looking into this redrilling of the mount and after checking mine out I seriously wouldn't be redrilling it, I don't think the new point is even on a flat surface and would be extremely close to the edge.