If i went to the gas station and used their air compressor what tank can i get?

Also if I want to reduce a 3" pipe to 1" or 2" what part should I use?

hi guys, I am working with imthefreak on the hybrid and I am having a very finding the necessary parts. Some parts I am having difficulty finding is a threaded 3" aluminum sch40 pipe converters for the valves and barrel a cheap air tank We live in San Jose btw but I am fine ordering this stuff onlin...