I need a donor section of rear firewall. I have all the other sections from Restoration Design. Mine has several 1/2” holes that rusted because of the firewall matt inside the engine compartment. My plan is to lap seam spot weld over the diseased part and then excise the rusty cancer.

Got the same issue! Honestly, IMHO, all you need is the correct gauge sheet metal to fix these small holes. I'm currently restoring this same area on my LE. I will be starting on these repairs next weekend. This is what you get when you store a car open to the elements out in a field I like your problems better .

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What did you use to strip the paint down to metal ?

Paint in this area is usually pretty easy to get off. With that said, there are many facets/areas of odd shape so you need to get creative to get to the paint. Before using a chemical stripper, I'd try just a scrapper. I had areas where it came off with very little effort. Other areas required a wire wheel (see angle-grinder in pic). Chemical stripper is your other option but it's not what it used to be with all the environmental restrictions on the "good ingredients". You could used the paint remover first and then go with the wire-wheel but this gets a little messy. Here's a pic of me getting underway. You can see how bad mine was. Yikes! I did use Map gas to heat up the sealant at the bottom (watch the fumes). This makes it come all come off quick. Don't be afraid of just diving in on this section. It should only take a few hours.

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