I think my fix is a little easier and no welding involved. 1/4" x 1 3/4" steel, maybe 6" long. Drill and tap for a short cap screm ( allen head type.) Then drill a hole at 1.5", 2", 2.5", whaatever, making it adjustable. As long as the holes sit under the axle saddle so they get locked into place with the U bolts. Your choice whether you want to make it fit over the center bolt or so that a new center bolt goes through it. A similar hole should be in the bottom plate to match.
If I didn't have access to materials, machines, welders and plasma cutters, I'd probably get that Chevy Duty kit. However, I can make my own. I'm not sure about that lug nut idea, wouldn't the nut be too big??
Maybe I should explain my set up. The original torque tube axle is long gone. It had a later 3/4 ton axle with a four speed, so the driveline is open from the pillow block. Out with the 3/4 ton, in with a 10 bolt. New saddles under the axle, over the springs. U bolts over the axle. Spring plate under the spring pack with provisions for a shock. And that should do it! BTW, I'm upgrading with 1978 Cadillac Seville rear discs.
There will be some welding involved but not on the springs themselves. I've removed the 3/4 ton axle so far and it looks like the spring bushings will need some attention. I didn't want to do this, but I think I might remove the body so I can have some real access to work on the frame. Plumb and wire everything new front to rear along with cleaning and painting components. Makes it nice that I have a 6 ton overhead crane to use!! Sorry, I almost started bragging there!
