Cut back every compromised section — don't try to save metal that's given up. Use your angle grinder with a cutting wheel and work methodically from the obvious rot outward until you're landing cuts on solid, uncompromised steel. Your new panel is only as strong as what it's welded to.

• Cut 1–2" into solid metal to ensure a clean weld zone
• Mark cut lines with a marker before grinding
• Save the old panel — use it as a template if needed

A clean weld starts with clean metal. Wire brush or flap disc every surface that will see weld heat — paint, rust scale, and factory undercoating will all contaminate your weld pool. Apply weld-through primer to the mating flanges before the panel goes in. This is the step most people rush. Don't.

• Bare shiny metal on weld zones — no exceptions
• Weld-through primer on both mating surfaces
• Vacuum out all debris — fire hazard underneath
• Check for hidden rust further up the floor structure

Fit before you commit. Drop the panel in and check every edge, every flange, every body line — before a single clamp goes down. Our panels are manufactured to match factory contours, but every chassis is different after 30–50 years. Trim and massage the edges until the fit is right. You're building it once.

• Check factory body lines match across the panel seam
• Mark overlapping areas with a marker before trimming
• Use an air body saw or nibbler for precision trimming
• Panel should sit flush — no tenting at edges

Clamp, tack, check, weld. Tack weld every 6–8 inches first, then verify the panel hasn't moved before you lay down your full seam welds. Work in short stitch passes — never run a long continuous bead. Heat is your enemy here. Let each weld cool before moving to the adjacent area. Warped floors are the hallmark of impatience.

• Tack every 6" first, verify fit, then stitch weld
• Skip around — never weld the same area twice in a row
• Keep passes short: 1–2" at a time, then move
• Grind flush and re-check for pin holes before sealing

The weld is done — now protect what you built. Grind the top side smooth, apply seam sealer into every joint and seam, then coat the underside with a quality rubberized undercoating. Inside the cabin, treat the bare metal with a rust encapsulator or etching primer before your finish coat. You did the hard work — don't let rust undo it.

• Seam sealer on every joint — inside and underneath
• Rubberized undercoating on the exterior floor pan
• Etching primer on interior bare metal before carpet
• Let seam sealer fully cure before driving