If the cranks are 1 piece it's a 1/2" pedal. It requires a 15mm open end wrench to remove. I wouldn't spend any more money on an '80's Huffy than replacing the pedal.
No wait! I wouldn't spend ANY money on a Huffy that old!
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"Life is not a journey to the grave with the intention of arriving safely in a pretty and well preserved body, but rather to skid in broadside, thoroughly used up, totally worn out, and loudly proclaiming, "WOW, What a Ride!" - unknown
"Your Bike Sucks" - Sky Yaeger