[bagged78]

Well you have two choices,
1. 25 gallon
2. 31 gallon
I have each one, and the only differance that I can see is when looking at the tank from the rear of the Blazer the 25 gal. seems to be level ( by level I meen from the flat piece that sticks out from the middle of the tank down to the bottom) and the 31 gal. seems to have a slight taper.. That may or may not be acurate but it is what I can see, and ever one that sells gas tanks lists them as 25 and 31 gallon tanks, and no other options..
Hope this helps, I guess you could assume that your tank is only 25 gallons and if you have a 31 gallon you would be safe....