All paint companies sell different qualities of paint. The coverage of each quality in each brand will not be the same. Even the color choice between brands can make a difference. For example, some paint brands have very good coverage with their yellows, but their red's are not as good as some competitive brands/qualities.
A friend of mine painted his Model A (not including the fenders!) with Omni and it took 4 quarts because the color is a maroon and Omni doesn't have good coverage in that particluar color so he spent far more money and time buying and spraying several coats to get the coverage he needed. The cost per quart seemed reasonable, but having to buy 4 quarts made it more expensive than if he'd just bought the Envrio Base instead.
My point is that unless the OP goes to a paint store with knowledge of the color he wants, there's no telling how much paint he needs.
