I have a half ton 07 Silverado new body with a 26 gallon gas tank in it. I recently did some digging and it looks like its not expensive to buy a 34 gallon tank and was interested in putting a larger tank underneath. I like the idea of putting the 34 gallon in like the 3/4 tons have but not apposed to go bigger. Has anyone done this or looked in to this to see whats involved or if it can or cannot be done?

Looking around it appears that if you have an extended cab or larger and/or a 6.5' or larger bed you might have factory options available to do this.

It'* a crew cab with the 5.5 short bed

From what I saw out there probably not, at least in a "factory parts bin" sense. Could be worth a look though, maybe it would fit partly under the cab . . . ?

I want to take the 26 out. Put 34 in. The 3/4 ton has it. What would be the difference.

Frame rails might have different dimensions, and perhaps different things are mounted there. I'd suggest crawling under one while yours is next to it and compare. Bring a measuring tape.

1/2 and 3/4 tons have different frames,bed lengths,wheel base differences and I believe fuel tank strap locations