the 3 prong auto unit: the two outer terminals are to power up the white backup (reverse) lights at the rear of the car (connects power up front (not sure from where, HL sw or ?) to rear lights) and the middle terminal grounds the NSS when the trans is in neutral or park so it will turn over. I ain't a stick guy but I am assuming the (2) terminals on the manual trans are for the same backup (reverse) lights and that the NSS is either grounded by the clutch pedal or it is grounded right there at the NSS switch itself (to the case). EDIT connect the (2) outer wires in the "auto" harness to the (2) outer wires in the manual trans connector on the trans however which way you choose to do that (cut/splice/solder) then ground the NSS "grn" terminal right there at the NSS switch to the metal case & just be aware that this defeats the safety feature & it will now crank in any gear. No biggie for most of us but I gotta throw it out there. You wont be using the middle wire in the "auto" connector as you are grounding it upstream (at the NSS switch) as opposed to the automatic trans grounding it when in park or neutral.