How much Paint

Much appreciated! I will give them a call on the per gallon price. I think what @DesertRat said is a good idea, buy what the whole car will take now. From what I have been told unmixed (no reducers) paint will last at room temperature for quite some time (years, I think) I'll be sure to ask when I call.

I called TCP Global to get some info and the guy that answered seemed less than sure about his product or the answers to my questions. SPI one the other hand was very knowledgeable.
Yes it can happen. When I bought the paint for my barracuda I just bought a qt. to do the engine bay. Then about a year later a bought a gallon to do the rest of the car. It ended up being a shade off. I ended up having over a grand in just paint material.