I'm going to go with what everybody else is saying here. Run new wires. Get somebody else to do it, because in an old house, it's disgusting work. Spiders, crawl spaces, rat shit, etc. The old rubber and cloth covered garbage you no doubt have are going to burn your place down, and the duty cycle of an EV charger is pretty relentless. Three days or whatever at 12 amps to charge your car from empty? Ridiculous. Who needs that?
There's a chance that your wires are run through rigid metal pipe, which is usually grounded, provided no mickey mouse electricians screwed it up in the past, and those pipes are a good insurance policy. On the other hand, the best grounds are to water pipes and 8' rods driven into the earth. Problem is it's so damn dry in California. You can get an 8' copper clad steel rod for $12 at Home Depot. Good luck driving it in without driving yourself insane.
IF I were in a pinch, and needed to charge my car, I'd put in a new receptacle and ground it to anything and everything I could nearby with a nice big fat wire. Galvanized or not. Not the right way to do it, but if it's the apocalypse, I'd rather have the body of the car at the same potential as the water pipe. And about those rigid pipes? If you get full 120V between the outlet's hot and the metal housing of the box, it may well be grounded already, though no guarantee it's a low impedance path (in other words, it could be a crappy ground) but it's likely better than nothing. In that case, the simple act of putting in a new receptacle will give you a half-assed ground connection. Save yourself the headache though, and slam in a real plug. The Leviton 5842 is regular outlet shaped, but has a NEMA 6-20 and a 5-15 in the same body.
That way you could turbocord it OR portable it.
