Jeff, I'm a little unsure of your question, but I think if I'm reading you right, you are looking for a way to prevent corrosion in the areas you have cleaned and prepped for welding. There are a number of products available, all of them a "High Zinc" content. If you are spot welding the new panels in, as the factory did, all you have to do is coat the overlapped areas with this primer, and weld. I would advise you to use the brushable form of this, as the spray can versions rarely work. The zinc powder that is held in suspension in a spray can generally settles out, and when you try to use it, no matter how hard you shake the can, the zinc plugs the pickup tube, and you just sit there with a useless can of paint.
Using the "brush on" version, you can thoroughly coat both sides of the panels, and weld to your hearts content. The zinc conducts the electricity to the weld and the primer that is unaffected by welding serves as its own anti-corrosion barrier.
Jeff