Short answer, I'd consider these two vendors:
https://shootsteel.com/product-categ...steel-targets/
https://ar500targetsolutions.com/
For steel challenge 3/8" AR500 will be plenty even for PCC.
I'm not a richie, but I have enough targets from these guys to set up every stage (one stage at a time):
https://shootsteel.com/product-categ...steel-targets/
I also have my own plates for our plate rack made buy these guys - the ones the club leaves out get shot to shit.
They are all 3/8 AR500 and have had oodles of .22 up to .45 shot at them with no problems.
I've also found these guys to be good to work with: https://ar500targetsolutions.com/
After I retired I taught a couple of contract classes and bought my rifle plates (2/3 IPSC Torsos) and stands from them. Again, 3/8" AR500, and bunches of .223/5.56 at 110+ yards, no problems. They get a lot more use on the pistol side of things. I think if I bead blasted them and had them powder coated I could sell them for new.
When they started Steel Challange at our club they repurposed the cowboy action target stands for Steel Challenge. They are home made but I really like them because they are one piece. I hate shooting anything jacketed at metal hung on a wooden upright.
Here's a general picture. They don't tip over. If you are interested I could take some from different angles.