which fuel tank do i have?

[fordsrawesome]

Hey dumb question here but I have A 1983 250 reg cab and I need new tank straps for the primary side tank but not sure if I have the 16 gal or 19 gal I know I should just fill it up but its not my daily and I won't get to fill it up for awhile and they need ordered 2nite any ideas?

 

[dunk]

Short bed is 16 gal long bed 19 gal.