Fuel tank question

[Motornoggin]

I caved in my factory tank a couple of weeks ago, so I am on the hunt for a replacement tank and, apparently, a skid plate.
I saw that there were 2 tanks, a 13 gal and a 20 gal. From what I have read, they look identical. How can I make sure I don't get a 13 gal tank? Are there identifying marks or numbers that would enable me to tell them apart?

 

[old_man]

The only difference in the tanks is how the vent tube is routed in the tank and you can change that.

 

[Motornoggin]

Well then...no sweat. I'm going to do that little mod that gives you a 25 gal cap. anyway. Thanks.