MJ Floorboard replacement

My MJ's driverside floorboard is non-existant from about the pedals to the seat bracket, and rocker panel to tranny hump. I was going to bang in some sheet metal, but there's an MJ in the local yard with IMMACULATE floorboards. So, weekend project now involves me and an 18V sawzall cutting out as much of the floor as I need and overlaying it in my MJ (Eagle, don't panic...the rest of that MJ is junked and not worth much ). Should I use some kind of sealant between the new metal and my old floor where it'll be overlayed? I have mine cleaned back to good metal, and am thinking about 1" or so all around overlap, then tack weld it in and use automotive seam sealer around the perimeter, primer and some type of topcoating over the entire floor. What would y'all recommend I do, seeing as how the interior is gutted at this point and I have access to it all?
TIA,
Jeff

Joe R's father welded a new floor pan into my MJ for me and he welded it continuous. If you don't have a continuous weld bead on the outside (underside) you'll always have a joint where water, moisture and crud can sneak in and start the rust process all over again.