I think add co still makes one. Mine on my 83 are Hellwig, front and rear. The front and rear on my 97 are also Hellwig. On the 97 the bars are massive. 1-1/2" front and 1-3/8" rear. I forget the dimensions on the 83, but I want to say 1-3/8" front and 1" rear but that van is 1,000 lbs lighter.
I ordered a Hellwig for the front but they cancelled the order because they said they weren't making them anymore. Idk... Seems like a shame we can't get aftermarket parts for these things.
I thought I read somewhere that the Addco rear sway bar want very effective because it wasn't big enough... Can't remember where though.
So measured the Hellwig bars and they are BOTH 1-1/8". Sucks forgetting things you last worked on 15 years ago.
The factory rear bar on my 99 OBS Tahoe is 3/4" and my brothers 99 OBS Suburban had the same bar. My Tahoe has the 1-7/8" factory front bar and my brothers Suburban had the 1-3/8" front bar. Both 2wd setups. Tahoe has alot less body roll than the longer/heavier suburban. GM did some dumb things suspension wise. My Tahoe was a LT model with the Z-56 suspension option which was the same as a Police Tahoe or Limited and also ordered with the upgraded brakes from the same model. Tahoe also came factory with aggressively valved Bilstiens although they have since been replaced by even bigger piston KYB Monomax shocks. Larger bore master and larger 8800 GVW front calipers with the 2.75" wide rear drums. Suburban had the smaller front brake calipers on it. IMO ALL of the GM trucks, SUV and van models should have had the largest front calipers avaliable and hydroboost but that is just me. Shortest stopping distance possible is a good thing. The fact GM still builds a 2022 Express without even a rear sway bar should be criminal!
After researching the Addco I'm not impressed with the way it attaches to the springs. I think I'm going to try to modify a BMR GM A body anti roll bar that mounts to differential tubes and frame:
