Summer means overheating threads, lol.
First step - verify your temps. Are you really at 214? Infrared thermometer or mechanical temp gauge help confirm this.
If your temps are accurate, then solving idle overheating is usually pretty easy. If you cool down at speed, then you just have insufficient airflow at idle. Are you using an electric fan, or a factory shroud and clutch? If the former, then electric fans are iffy on these cars - the ONLY one I've heard nothing but good reviews about is the Flex-A-Lite #295 dual 13.5" fans. Outputs 4600 CFM at full blast, but puts a hell of a draw on the alternator so you'll need to upgrade your alternator. That is the only e-fan I've heard of that actually cycles on and off like a modern car and will reportedly suck an empty beer can out of your hand. It also happens to seal and fit *PERFECTLY* on a second-gen radiator.
But if you're still using a stock shroud and fan clutch, your fan clutch may just need replacing. Don't even bother "testing" it. Just replace it, maybe with a Hayden HD version (part #2747). And I certainly hope you are using a shroud. Shrouds exist for proper airflow at idle.
And then finally as mentioned, ignition timing. A 461 stroker, I'm guessing you have a fat camshaft... all the more reason to throw in a ton of timing at idle. This can be accomplished with a vacuum advance hooked to manifold vacuum, as b_hill mentioned, since obviously putting the initial really high will cause starter kickback. A factory '79 W72 had around 36-37 degrees of total timing at idle with vacuum advance hooked up, since the vac advance received metered manifold vacuum through a calibrated modulator valve. If you're not running vacuum advance, then your ignition timing is probably way too low for proper idle cooling. High timing = cool idle, and it's not a problem as far as detonation is concerned because there is no load on the engine during idle, and the moment the throttle plates open up wide, vacuum advance is gone, anyway.
Try those things and see how it works out for you.