I just went through a similar situation. Ultimately I trashed an old
tank for a new 26 gallon tank I purchased for $75 at Cummins with a
drain cock and a check valve already installed. You really have no idea
what condition the rest of your tank is in. Anything special about the
tank that you just wouldn't replace it with a new tank? Seems like
you're throwing a lot of time and good money at something that should
be replaced for safety reasons anyway.
-M