Everything reads as normal in your first post. As Phil says the original rad is a good one for its size. If it has no leaks that's even better. If you do remove it for back flushing You may find that some of the fins have started to rot away. Not uncommon but isn't good as it reduces the amount of heat they can disperse. Fin rot can be quite bad so don't be tempted to give the core a quick blast with a pressure washer to clean out the bugs, that will only rip the corroded fins off. Make sure your rad cap is good and of the correct depth. It's only a 4 lbs psi one as standard but can be upped to 7lbs. This will put a bit more strain on the rad so keep that in mind.
The Corvair and most modern cars use an air blend system to control the heated air. Moderns with a fixed temp heater matrix. Amazon uses variable heat by controlling the amount of hot coolant that flows through the matrix along with an air quantity control. It can be used to help with an little extra cooling in an emergency. Perhaps stuck in traffic @110º!Using the heater now and then helps to keep the valve working properly.