Yes, it will be worth it to identify the symptoms more fully (i.e. what is overheating) before spending more money. Having a auto-dismantling uncle helps with the money part though!

What happens if you take the thermostat out completely? It's not like a Flathead V8, the A12 should run fine without it for a few days.

The other thing is are you using an electric fan? Be suspicious of that, even if it runs all the time. If the shroud, fan size, location & rotation aren't right, it can cause overheating. I once bought an impressive car at a bargain mainly for that reason. Put the stock fan back on and was back in business.

Mareo, though I doubt it's causing the overheating, perhaps you can find a good carb from a B210 or 79-81 210. It'll work fine, just make sure the idle cutoff wire is wired to the ignition.