Quick carpet question, need some advice fast!!

[danheit]

So I am going to be purchasing the Rock Auto carpet kit from ACC for my truck and I have a couple of questions. First, I am looking to order the carpet kit for NO GAS TANK, states it doesn't go up the back wall, but goes up to it. My reasoning for doing this is that I eventually plan on pulling the tank out of the cab and going with my 90 GMC tank that I have sitting in wait. My big question is though, is does the carpet that is formed for the trucks WITH the tank in cab include the tank carpet cover? Any reason why I shouldn't get one over the other? My plan is, worse comes to worst, I just cut the piece off that would normally go where the tank is if I never get around to swapping the tank out. What do you guys think??

Here's their description:

ACC Part # 17899718020MB 80/20 Carpet with Mass Back for additional moldability, sound deadening, and insulation Color: OE Color - Gunmetal Gray (22)
REG CAB 2 WHEEL DRIVE LOW TUNNEL WITHOUT GAS TANK; GOES TO BACK WALL. DOES NOT GO UP BACK WALL; MOLDED
* Stocked in outlying warehouse--