measure inside diameter of brake drum (where brake shoes touch drum) and measure outside diameter of brake rotors. usually if you look at wheel side of drums and rotors the size is stamped in millimeters on each
In order to determine the size brake line for a 1990 Ford T F 150, you will need to know the size of your drum wheel cylinders. You also will need to know what kind of disc calipers you have.
8"
You could have either 9 inch or 10 inch , depending on the brake drum size
3/16
7 mm
If your truck is equipped with 9 inch brake drums, you need 9 inch brake shoes. Many Dakotas were equipped with 10 inch drums and shoes though, so be certain which size yours is. The size measured is the inside friction surface diameter of the drum.
14 mm
30/32 mm
the size is 10.x2.5 or 9.x1.75 you need to measure.
Other than measuring it, any Auto Parts store has this information. The maximum wear diameter of the drum is cast onto the outside of the drum.
1/4 inch line, 3/8ths fittings.