air bags

I would be looking for one of these shops.

https://www.taraassociation.com/

Who would enforce this?
I didnt ask and they didnt tell when I had receiver hitch welded on the front of the frame. The weld shop has some sort of cert I am sure, but there is no "frame" cert I am aware of.
In general it is a bad idea to weld on the frame, welding will weaken the steel unless it can be heat treated, which it cannot. I had welding done on the front of the frame that was not an important part.
Anything between the axles matters, in front or behind the axle is not important to the handling of the truck or safety.
If you are welding on a piece that is in turn welded to the frame then it might be fine - like the end of a bump stop. Ask yourself, will the frame itself become hot to the point of becoming weak from the welding.