Is there a difference?

[crashman]

I am looking to install a on board air system but want to put a 5 or 10 gallon tank for air tools
My question is what is the difference if any is a portable air tank to one from viair or a on board tank they are both steel

 

[nevada]

if it has the connections you need, mounts, the correct size/shape, and is structurally intact(it will hold the pressure) then use it.

but, be aware, even a 5g is probably too big. its REALLY hard on the pump trying to fill a large tank. stick with a 2-3g.
also, physically, a 5g or bigger will take up a lot of space.

 

[crashman]

I got a dual compressor set up it says it can work up to 12 gallons I guess I can go with 7 gallons to stay safe