Do yourself a favor and spend some time on the phone with the owner at K&K. He is very knowledgeable, and loves to talk about the process. He suggested a spotweld cutter (basically a specialty drill bit) that made removal of a couple of my floor pans a simple, if not time-consuming job.
He'll tell you exactly what settings to use on your Mig welder, and even send along some scrap metal pieces for practice welding.
Of course, if the rust is just in a localized area of a given panel, then it probably does make sense to just cut out that part and patch. But otherwise, trust me, if you're going to all this effort, you'll be much more pleased with the final result by spending a few bucks more for the correct panels.
Even for small patches, it is best to duplicate the original factory "spot weld" construction by drilling weld holes every inch or so in the new patch (using the spot weld cutter again)... you'll have much less metal warpage to deal with. Then finish the repair off with a grinder followed by a good seam sealer, topped by a good rust-preventative coating (no need to do this again in a few years!)
I found an inexpensive ($39) power sheet metal shear at Harbor Freight, and it has been invaluable in getting the rusty parts out.
Phil
Oh, I did wind up with 3 extrusions I didn't need from K&K: Driver side floor pan, accelerator pedal attach bracket, and strengthening bar under the floor pan, if anyone's interested, they are out-of-the-box new, and can pass them along at my cost less the 15% k&k restocking fee.
Originally posted by psmith
Well my car just turned 40 and as a birthday present I decided to fix the rusty floors before my feet went all the way through to the ground Fred Flintstone style. So I spent the holidays pulling out the carpet and scraping the tar paper insulation off the floors. I like to think of myself as a "glass is half full" kind of guy, but I was not all that surprised to find more rust. Here are some pics.
...
With a little help from K&K I hope to be back on the road by spring.
Pete S.
Phil Auldridge
230SL soon to be 172 Metallic Grey/blue interior. Auto/AC