You will get every opinion in the world about which fuel to use. I will be crazy enough to start the debate.
Because you do not know a lot of detail history of the car, your least risky move is to use non-ethanol gas. Ethanol gas is fine if all the rubber parts in the fuel system have been converted to ethanol resistant materials. The limitation is that you do not know if that has been done.
Even though I gave my recommendation, don’t be overly concerned if you do not have access to non-ethanol fuel. There are lots of regions where you can only buy gasoline with ethanol. If that is your situation, use the 10%. All those people with classic cars who live in your area do it.
A big unknown for you is the condition of the fuel system. Depending upon the range of temperature and humidity where the car was stored there could have been water condensation in the fuel tank and lines. That could have created rust. The other concern is if the fuel has evaporated and formed a varnish or shellac type coating within the fuel system. My best guess is that if you have issues it will probably be due to the long periods of little if any use rather what gas you put into the car
I would not be concerned with the lack of lead in the fuel. You can do all the Googling you want and will get the full range of answers. My experience is that in these classic Chevy’s you do not have to worry about valve seat recession/wear due to lack of lead. The valve spring pressures are low as are the engine speeds. Plus I doubt if you will put 50,000+ miles on the car.
I’ll let a ’41 expert decode the body tag.
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