In 1974, I experienced an intermittent ignition problem that I finally traced to the cheap terminal box import. The two long terminal bolt heads had not been sunken deep enough into the plastic box so that the rounded heads arced against the firewall when the firewall go hot and expanded towards the bolt heads. Once the firewall cooled down, the car ran fine - for a while. Removing the terminal box in the rain on the German Autobahn, I noticed the arcing splotches on the firewall, right beneath where the bolt heads were located. Figuring that was why the ignition was cutting out occasionally (after checking and replacing EVERYTHING else!), I managed to screw the bolts into the plastic body just enough so that I could put some sealant on the heads to prevent arcing. After letting the sealant set up a little, the terminal box was re-installed and I continued on my way to Munich in the rain with no more ignition problems.
A fluke, you say, that could happen only to me? Nope! Since then I have traced ignition problems in three separate Model A's that were older restorations and incorporated some of those lousy 1970's import parts. Replacing these with the new higher quality terminal boxes solved the ignition problem in all three vehicles. The owners were flabbergasted at the cause of their frustrating misfire. I never see this cited as a potential electrical problem on diagnostic charts published in books and magazine articles, but it's a real possibility, especially in older restorations or cars that have been built since then using parts found in boxes that came with the unfinished Model A.
Add this odd one to your list, Bob!
Marshall
must have burnt a hole through requiring a weld to repair. that sounds scary 
