You've identified the problem you have shorted wiring. Sometimes that 80 year old wiring harness just needs to be replaced. I think I would do that first.
As to the shimmy - there are many causes for shimming but a couple of simple things you can get that often will solve the problem are -...
Many Newer long life anti freezes contain Organic Acid Inhibitors. I have read two published articles on them:
One says they provide good protection to lead/solder used in radiator construction.
The other article says they should be avoided as the Organic Acid base will weaken soldered joints...