What is a spotweld sealer? silcone, lead, soldier?

My 55-59 ASSY Manuel showing a spotweld sealer # 381924, sealing compound 466949. I found these # in my assy manuel sect 1, sheet 139

I am looking at replacing the cab rear skin as it is the only way to get the entire right side. Mine is severly creased all the way up the cab corner to about where the gas filler hole leval. It also has some buckling on the back of the cab, not to bad there though.

Most of the spot welds on the door frame and 6 or 7 across the botton at the back of the cab are already broken. I can see light between the back /floor & it's obvious on the door frame/rear skin.

Thanks
Brad