<<<The manager said they might have been willing to pay for a>cheaper
aftermarket tank>>>

You DID not have a cheaper aftermarket tank that was damaged, it was a German
Tank.  They have the right to put back on WHAT WAS on the van to begin with.

The aftermarket tank does not have any filters in the tank or baffles.  The
German tank has a prefilter inside the tank along with baffles (small but
they are there)

Plus you have lost a lot of your tank capacity and it IS dangerous...

Robert