uiblog,
1. The photo attached in your previous post lists the power supply having both G1 and G2.
2. Did you make a complete search for the G2 pushed in between, behind, inside, or under something else? Did you trace the G1 back to the power supply?
3. I can not think of any possible reason the previous owner or the seller would remove the G2 connection. That would be done by cutting wires off at or inside the power supply. Also, it would have cost HP far more to make both a G1 only and a G1 + G2 version power supply than to simply have all 600W z420's have both connections. < Very unlikely.
4. If you are convinced your system does not have he G2, then the Molex to 6-pin plus the 2X 6-pin to 1X 8-pin should work.
BambiBoomZ