Anyone able to locate part numbers for the 36 gallon tank on the 22 models? So far most of what I've seen says 15-20 or 15-21. I can't even get a part number from the Ford Parts site. Doesn't seem like they'd have revamped the tanks with the minor differences on the 22's. My 17 had the big tank and it is so nice not to have to stop for gas more than once a month that I'm hellbent on adding it to this truck.