Hi Len, it sounds like 350 would be hard on the rear unless it's total for both. I measure the wire on the coil springs. I like the 7/16 rather than the 1/2" for ride quality. It sounds like the shocks aren't working if you're adjusting them and not seeing a difference. If you look at the outside of the rear arms and hubs there is nothing stopping the forward back movement under the fat tired high HP application we use them in. It does help handling some on stopping flex and toe change on the rear but mostly is peace of mind and durability in this application. I think you're on the right track with the rear getting shocks, springs and ride height dialed in. The front torsion bars work well but an upgrade on them is considered the coil over conversion.
Welcome to Lesher Motorsports
Do you have the manual for your car? If not shoot me an e-mail address I can send it to you. That will help you set it up. That's a really good looking CCX you have there.