How many gallons is my gas tank?

I have 1976 Ford F-150 all original parts and need to know how many gallons it is it's the orginal gas tank thanks

One usually finds that out by reading the car specifications in the owner's manual OR filling it up.

My WAG is 16 gallons. I checked a couple of online parts houses (you too could do that if your google wasn't on the fritz) and they show that the replacements are 19 gallons.

I had a 1970 and its fuel capacity was 17.5 gals in the main tank and the rear tank holds 19.2. (if you have a reserve tank)… It should be the exact same for your truck.