Junk it or fix it? 89 c3500 rear suspension under my school bus Q's

[BBEEP]

Ok here goes: I am at my wits end with this. This project is a 1989 C3500 Chassis under my 1952 "White" School Bus. I had a shop in Portland do some work on the suspension and it just doesn't work.
I asked for the truck to be lowered about 6 inches. I asked for "helper" bags only, so that if I towed an enclosed trailer with 20 people I would be fine. I posted some pics.
When I got the truck back, it was a butt clenching ride home. A couple things, the rear swaybar was left off. The bags are rated 1500 lbs, one in front of the diff, one behind it, securely mounted to the frame on the top of the bag. The bottom of the bag was mounted to a bracket that merely surrounded the helper spring. By the time I got home, the rear bags had slide backwards at the spring mount 4+ inches!!
At first I connected a chain between the two lower brackets but have since made a bracket as you can see from the pic.
The problem is, it drives like a 52, swinging its ass-end as I drive down the road. IT SHOULD DRIVE LIKE AN 89!! HELP!
Should I junk it and buy a new Ride Tech or similar 4 link? or ???
And is the C-notch safe or too short?