Clarification here.
I have not at this time installed a W8 rear tank into my car.
A few facts on the W8 tank.
1) It will only work on 4-motion cars.
2) the trunk floor-pan where the spare tire goes must be replaced.
3) The tank is really nothing more that an add-on to the stock tank, although the stock tank must be replaced with a W8 unit that has the additional hose fitting for the add-on tank.
4) there is an additional electrical unit that has to be wired in for the fuel level and transfer pump to work.
5) cost of all the parts less labor would be in the $2000 range.