GT Tommy

Does anyone know what must be done to install an after market fuel level gauge in a 2003 GT Mustang with a 4.6 engine? I'm concerned about the specific's of the wiring! I would think that the current wire(s) attached to the factory fuel gauge cluster has to be cut off somewhere and isolated from that gauge, is that correct? Would that interfere with the function of anything else in the cluster? Does any one have an electrical schematic for that circuit showing the exact wire colors and numbered circuit's? I just replaced the fuel pump module in the fuel tank. I yes, I did not bend the float arm which would give a false reading. I was very careful with the installation of the fuel pump module. The gas gauge was giving us problems (false readings) before we replaced the fuel pump module. The fuel pump was burnt out, that was one of the reason's for replacing the fuel pump module assembly. The other was I had hoped that the new sending unit on the fuel pump module would have corrected the problem for the current gas gauge readings. At a full tank, the gauge is reading 3/4 tank. Thank you for your support, Tommy.