I've often wondered about the wording in the rulebook regarding fuel tanks and fuel cells.
Apparently a racer cannot alter the stock fuel tank for Stock Eliminator. (last sentence)
However, the stock tank can be replaced by an aftermarket cell up to a maximum of 16 gallons.
That's a big difference there. lol
From the 2014 rulebook:
GAS TANK
Must be correct year, make, and model for car used, with stock fuel
inlet and outlet locations. Must be in stock location; fuel line and
pickup may be resized. Fuel cell permitted; maximum capacity 16
gallons. If fuel cell is used, OEM gas tank must be removed, and a
firewall of minimum .032-inch aluminum or .024-inch steel must be
installed to totally seal driver compartment from fuel cell. Trunk floor
may be modified to accommodate fuel-cell sump. Where OEM gas
tank is in the trunk floor, area occupied by OEM tank may be
replaced with material equal to or heavier than OEM floor. If OEM
gas tank is used, it must remain unaltered.