Really it is the std cab short bed vs the rest of the configurations.
I think the Ext Cab short beds and the std cab long bed are close to the same thing in the frame/tank area.
Look at the space, look at some of the other available plastic tanks out there and start comparing.
I haven’t had enough experience with gas tanks before so I can’t help but I was looking at a tank for the rear of the frame to replace the spare tire, an aux tank, it would require a second fill and electric off/on select valve.
Sorry I can’t help more, start measuring and comparing.
4x4, 5sp, Std Cab, Stepside, E4 Red
4” Lift - Coil-Overs, 6” SkyJacker Leafs - No Blocks (Mistake)
31 Spline FX4 Rear Axle, 4.56s and OX Locker, Hurst Shifter w/Optional Stick and "Made by Grev" alignment adapter