Those tanks, if original are really old. I have had two fail, an original on my 85 and a used replacement.  Then I bought a regulator and hose, an adapter that uses those little green tanks, replace my Dometic fridge with a compressor unit and now only connect a tank when I am cooking.

If I had the original fridge I would buy a new tank from a trusted supplier. 

When my last tank leaked at the filling station it took at least 45 minutes for the propane to vent. The very pissed off attendant stomped off and simply said don't smoke and don't move. Thankfully he didn't call 911. I got to sit on my butt and consider how bad an idea that this was.

Ironically I had previously obtained a letter from the propane regulatory agency that said in Ontario the van at that time was exempt from inspection regs as it was not a propane powered vehicle. I think that regulation may have changed.

Both of my failed tanks developed pin holes under the tack welded  Manchester ID tag.

If you need a big tank buy a new one. If you think the fuel injection hoses/fittings can dot your van in remember that as Dennis said gasoline is very picky about explosion  compared to propane

Ian