Sorry, but you're outta luck there. I don't think they added them until 84-85.
Basically, you have three choices:
1. Remove the gas tank and dump it out. This has the added benefit of allowing you to clean the tank (possibly take it to a radiator shop to have it boiled and sealed, not too expensive) while you have it out. You can also clean up any rust spots and undercoat it to help it last a bit longer.
2. Remove the fuel line from the carb, aim it toward a bucket, and let the pump run the gas out.
3. Bust out the garden hose and try to siphon the gas out without swallowing/inhaling any of it (I don't personally recommend this route).
Good luck man.
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