I'm one of those guys that used a mid 90s full size Chevy pick up seat in an AD cab. I'm only 6' tall but with the original seat my head was only about 4" from hitting the headliner and I'd strike my knees on the back of the steering wheel. With the newer seat I can straighten my left leg all of the way out if my foot is next to the dimmer switch and I have lots of headroom.And as Mike B pointed out you will gain nothing by removing the fuel tank from the cab. The seat moved all of the way back will rest against the cab before it will contact the fuel tank.
