Knocking noise Question

[Platinum00]

Alright all I have had this knocking noise I thought was coming from my suspension. I was just about to upgrade it all anyway so I wasn’t too worried. Well after the new suspension I still had the noise and it seems to be getting louder. I have located the knocking noise and it is not my suspension, it is the cab I know right. I attached two pics of where I am talking about on my extra cab I will be putting on later. My question is it ok to weld this together or is it designed like this to allow it to flex or whatever. The two pieces are knocking together it getting where I can just bounce the truck a little and they hit.