Long time since I posted here but I'm stumped on this one.I have a 2011 GMC sierra 4.8L ext cab 4x4 and the fuel pump is rusted out.I'm trying to find a cheaper alternative to the OEM pump but there are so many its hard to determine which is right.I have searched by vin# and have had dealers give me different part #'s for the same pump.I have narrowed it down to 2 AC Delco pumps MU2142 for the E85 fuel and a M100109.They are listed to fit my truck with the same VIN A and L20 engine code with the correct wheel base and box length.I know the truck is listed as flex fuel so does this mean I need the MU2142?The M100109 also lists as flex fuel.In the description of the two I did notice one listed with the sending unit(float guage)but the other isn't listing it.Are the two parts the same just one with the level guage and the other without?My OEM part according to GM using my VIN# says I need 19256389 which crosses over to 19257093.Can anybody help me out here?VIN # 1GTR2UEA9BZ390895.