Obviously the wiring all needs to be in good shape, with terminals well-crimped & soldered. Ditto re. the starter solenoid relay; just a "Ford fenderwell starter switch", or as they're known in the air-cooled VW community: a "hard start relay". I even put an extra push button, hidden under the dash, just in case the ignition switch does decide to puke its 'start position' function.
Also installed an extra 50Amp relay(& push button under the dash!) sending power to the the glow plug fuse, bypassing the oft-maligned factory relay... just in case.
J.R.
SoCal