It's on an A-body. I could find them on line separately, I walked by a set for $20 a few years ago at Valdosta thinking I'd never need them. Is it a common size box steel I can make my own out of or do I have to fab a box out of plate steel. I can measure tomorrow but I got to thinking about it while watching the game so not going back out to the shop tonight.

Thanks in advance, Kevin

the one set I saw made me think I would just have my welder buddy make em, looks like just simple right angles & use thick material/reinforce everything good

Use 3/16 sheet and you're good to go. Have the sides bent down from the top and weld on the end plate. 3/16 will bend nicely. If you try to bend 1/4" it will have stress cracks. 1/8" is too light.

what about using thicker material & cutting it to avoid stress cracking

Why ?!?!

3/16" is plenty thick. Also, you have to weld it to the thinner frame. The thicker the material the harder it is to get good penetration on the thick without blowing through the thin.

US Car makes a nice set.They bolt up and position the boxes where they should be.then weld in.I have a MP set for the 65 but just might buy the other set.Rocky

Ok, but if 1/4 will stress crack when bending I was thinking what about using 1/4 & cutting it instead of bending it then (re)welding it but if 3/16 is thick enough then moot point, we should go with 3/16

I have a set of those. I don't see the bolt-in advantage being worth the extra money as all that does is hold them for welding - something easily accomplished with clamps and tack welds. But IIRC all the MP sets are 1/8 material - the US Car Tool are 3/16. They're definitely beefy.

Thanks folks, I think I got what I need from a member. I would think 3/16 plenty think as well. Someone did a chicken job on a car years ago and I am going to make it right.

Even 1/8" is plenty - as has been mentioned, the M/P ones were 1/8". By the time you are bending those you probably should be running ladder bars or a 4 link anyways.

I've used three different sets of the Mopar kits on two B bodys and one A body. I have had them installed (I'm not a good welder, yet ) with the outside edge welded into the outer subframes to get max inset, the first set in a B bodys was centered like Mopar shows them and the last set in my 1969 Dart GTS is welded so the inside of the box is welded into the inside of the subframes to get better leaf spring clearances on the passenger side to the stock gas tank

We rarely cut out the outside of the frame rail, which moves the springs in the max amount. Granted, with the spring not being centered under the frame rail, you need to use offset shackles, which is easy enough to do. I probably haven't installed an actual "box" in the last 10 or so I've done - I simply shear 1/8" plate to weld in for the top and front, and trim a new side plate to mirror the outside frame rail. It isn't an issue with stock style bushings that have an inner liner to tighten the front bolt up solid, but with springs that run a solid front bushing, (and you leave the bolt loose and lock-nut it) I weld an 1/8" washer or plate to the sides to keep from beating the holes out of round.