In my conversion of my '69 factory A/C to VintageAir, I cut a large sheet of 20-guage steel that covered all the old holes in the firewall and welded the plate on the inside of the firewall. I then went to the outside and completed the welding, and made a small plate to fill in the old blower motor hole in the fender well. Finally, when I am ready for primer/paint, I will complete the job by using seam sealer over all of my welds so they can't be seen.
