Will boxing the upper and lower control arms help stiffen them up like an after market setup or is it a waste of time?

It is not a waste of time. It is a useful upgrade and offers improvement over the straight stock setup for alot less than some of the aftermarket bolt in tubular setups. If you need new arms and don't feel like doing the work yourself you can buy them like this from opentrackerracingproducts.com

I could tell you the secret things only a handful of stang guys know.
But Im a Bears Fan

Please don't hold the pack against me.LOL

Boxed arms aren't as strong as tubular stuff, but they're far less expensive and still reasonably light. Boxing in the arms is definately a worthwhile invest ment of time and money, or like dodgestang said, you could buy them that way. Boxed control arms are enough for most people, and unless you're really wanting a badass suspension setup on a restomod they'll do very well. If you wanted to get really fancy you could cut gussets that you could insert at angles inside the arm and weld those in and then box it, the arm would be stiff as hell.

I've found they don't fight back much. Better to pick on humans.............................;)

If you have the skills to do the boxing, why not make your own tubular arms?

Jav