WOW i have never seen the "visitor messages" page until today. i am not sure if i have an 85 cyl mustang pump, but it's Master Brand Electric E2025 retrofitted as you described. yes, only one line into a in inexpensive holley fuel pressure regulator, non-return style. i believe if you have a return line, you can still use the EFI pump as long as you get the correct pressure regulator. to my understanding, EFI fuel pumps have the ABILITY to make high PSI, it will all depend on the fuel pressure regulator.