This past weekend i removed all of the rear seats and flooring of my conversion van and noticed that I have 2 bad rust spots right by the Wheel well from the inside. The one side has a large hole about 12 inches by 3 inches.

Here are some photos with the interior removed - https://photos.app.goo.gl/vp46apRjD7SqNyEs6

I want to fix the rust then paint the floor over to stop the spread of more rust in the future, lay down insulation and then flooring.

Any suggestions on how to tackle this rust problem before I move forward?
Thanks!

 

Cut out the bad sheet metal and weld in new. You can get the metal from sherman It's listed as a cheby part but they have it as universal also(part # 897-77). Or get it from a donor vehicle in a junk yard.

 

You need to cut the steel out and the preferred repair method would be welding. Does the rust extend down into the "frame" rails? This vehicle is a unibody so the frame cannot be replaced completely.
Realistically, I would not bother welding unless you have structural issues with respect to the frame rails. Structural work requires some level of competence and preferably donor parts from another vehicle due to it being a unibody.

Steps for non-structural work would be:

• Fix any water leaks causing the rust
• Cut out the rust and go about 1" past the edge of the rust to make sure you got it all. That may include opening up some overlapped metal around the wheel wells but you need to get rid of the rust.
• Grind suspect areas to bare metal
• Make some patch panels that overlap about 1" all around (do not worry about the contours of the floor)
  • If you want to match the contours of the floor you will can make them in a few ways
    • Buy the parts pre-fab if available
    • Bend the panels using a brake
    • Router the pattern into hardwood, cut out a piece of steel strap to match the routed hardwood (less the thickness of the sheet metal), and pound the bevels into the panel with a hammer using the steel strap and wood pattern
    • Use a bead roller
• Spray Prime
• Spray Paint
• Apply seam sealer to the opening where the panels will overlap
• Screw the patches on with self-tapping sheet metal screws
• Cover it up
• Go under the vehicle and touch things up as necessary using leftover paint and seam sealer.

Perhaps you should prep it as best you can and then have a mechanic take a look to see if the workmanship will be acceptable from a mechanical safety point of view.