In replacing my sending unit on my 91 LWB, I noticed when I pulled it out it was pretty rusty. When I shined a light in the interior of the tank wasn't very cleaned. My question is are replacement tanks available? Has any one put in an aftermarket tank? Has anyone tried repairing the tank? I have seen several products like POR 15 and Eastwood has something too. Any success with this type of product or stay away?