sounds like you're over thinking this. hook it up as it was it was. When I did my first EFI swap 15 years ago I found all my questions/answers in a factory shop manual. to give you a short answer: most inputs/outputs from the ECM are ground. ECM does not require VSS, but if you want TCC control you will need it. I don't understand about simplifying the fuel pump circuit? A relay needs power and ground to work. usually one would be battery or ignition voltage and the ecm grounds the other to active the relay.