My floors are rusted out on both sides so I got new pans from Summit that fit pretty good with a bit of massaging. I’m going to weld them over the old floors is there anything like undercoat or bed coating that I should put between the old and new?

 

Cut the old floors out, otherwise you'll have a water trap between the two floors and the new ones will start rusting quickly. Just my two cents.

Pat

 

Welding old over new is a terrible idea, just going to make a rust sandwich and spread the rust. Cut the old out and treat all the areas with rust converter and do it properly.