The Clarke tank is street legal in AZ, mine went through emissions with it. But even if it weren't, and you have yearly inspections, just keep the stock tank, and swap them out once a year. The Clarke tank is worth every penny. It makes the XT actually useable for extended back country trips.
I won't spend more on a bike than I think it's worth, but if it's a good deal, I don't seem to have a problem buying bikes I don't need.
2002 Vulcan 750, 2013 Royal Enfield B5
2001 XT225, 2009 Genuine Stella
1980 Puch moped