[HoosierDaddy]

Assuming yours is a poly tank, I would advise replacing the tank depending on the extent of the damage. You don't want a leak in your newly refurbished bay. There were a couple places building tanks for the Bus conversion guys. I cannot find them at this time. When I redid my bay, since I had the tools available to me building one out of steel was a LOT less money. However in your case probably a poly tank is the best choice, especially if you want to add a tank monitor. I installed a dump fitting on the driver side only. That allowed extra room for extra tank capacity. Here is a link I found on a Google search.
http://www.watertanks.com/products/RO-RVB455