It's only a 1 pound tank (http://www.amazon.com/Worthington-281149-1-Gallon-Cylinder-Prevention/dp/B000SKX63U). With drainage holes in the area around it in case of a leak. In the end, it will also be in its own box with direct drainage so that there's no chance of leaking into the rest of the van.
Rest of the stuff, can do. Thanks!
I bought a Worthington tank off Amazon (https://www.amazon.com/gp/product/B000SKX63U/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8&psc=1). Unfortunately, it is not pre-purged.