Light Air Tank

You guys need to think here. Old tanks can be dangerous. If you insist on using this rig yourself a backyard HYDRO (that's water, not air) pressure test. I'd go at LEAST 2x or preferably 3x the air pressure it will see. Fill it completely with water, then use "some other method" to generate the test pressure. Air/ CO2 whatever is safe once the tank is full

Consider buying a CO2 bottle. CO2 is liquid and therefore contains, effectively, a LOT more volume.

Small air tanks don't fill much in tires. Something like a 50lb freon tank will fill 2 typical flat passenger tires enough to move it but certainly will not take both to full highway road pressure.