how mnay compressors?

i was just thumbing through an old issue of MT and saw a taco with 4 Viair 450's. Well I got a total of 5 450s that are all good, but I wanna run 3 of them on my Mazda with a 5 gallon tank. I have been told my alternator wouldn't hold 3 of them. Is this true, or can i do it? If so, how would I go about it?

It depends how big your alternator is... how many amps?

stock.... I don't know. I thought about making a bracket and running two alternators. would that help if my one ain't enough?

I would probably look into buying a higher amp alternator instead of adding another stock one.