I've got a 76 Cheyanne. When I took apart the dash, somehow the gas guage got screwed up. I know I get about 10mpg but need to know how big the gas tank is to know how many miles I can safely go on a tank... So, how do I tell what size the gas tank is (other than running it to empty)?

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....

I beleive that is an accurate description in the difference. You could also just run it low and fill up, and see how much it holds.

So, would this one be a 31. My sticker in the glove box says that it has the 31 gal, but I have let it get pretty low and I have never put more than about 25 gal in it. Maybe my gauge is a little off?

any ideas?