Jim, I agree with these guys:
Ask Jed Zimmerman. He is very fair and he does beautiful work. Jed makes your seat foams, too. Lots of our members have been very happy using Jed's products and his advice.
I don't add anything to my unleaded gas, but I had hardened exhaust valve seats machined and installed into my '59 heads. This applies to ALL engines built before 1980. Especially if you take your car on long trips.
They re-formulated our modern engine oil to conform with catalytic converters. Problem is, they took out an important ingredient that is essential to our flat-tappet engines; ZDDP. Look this up on the internet for a full explanation.
Ray is right about your radiator... it's made of brass and copper, and WAY better for cooling than aluminum and plastic. A recored original radiator cools much better than a new aluminum.
I have a question for you: If you bought your Squarebird in Denver, does it have 'lean' jets in the carb? This is VERY important. Don't let your engine run too lean for long. - Dave