Recently I was unable to obtain a floor pan right rear quarter--the good
heavy kind with the flange for the blots at the heater channel--and because
I need to get this project completed, have resorted to one of the smaller
Brazilian pans, where they are put down over the edges of the old pan. In
other words, the old pan quarter is cut out and the new one welded in at the
edges.

I would appreciate any advice regarding:

1. What to use to make the cuts--I have an abundance of cold chisels, etc.,
but no air chisel.
2. Whether to gas weld or wire-feed (gasless) weld the edges, and whether to
use a long continuous bead of weld, or spot weld. (I'm concerned about
moisture getting past this joint and starting up the rust again.)

Thanks for all input!