Same problem here
I had the same problem on my 96 3500 due to prior tailgate issues. I was going to weld to but I think that the heat cycle would possibly make it weaker. So instead I just used a piece of 3/4 angle aluminum verticlly. Drilled holes staggered from bed bottem to bed side. You can nut and bolt it easily, just remove the tail light assy. 5/16 fine bolts with flatwashers and nylocks. Would be glad to take pics and sendto you. Hope this helps.
Eric