Since the engine harness was on the front seat when I bought my car I need to know how these were originally installed (or can be installed). Obviously the passenger and engine halves are held together by the thru bolt in the center of them, but how were they attached to the firewall? Was it just the two tiny clips that held the passenger side connector to the firewall or did they run screws thru the two hole on either side of the square hole the connector went thru? If they used screws thru these holes what size and length were they (I'm thinking M4)? The reason I ask is one of the tiny clips on my inner bulkhead connector is broken so I'm going to have to use the two outside screws to hold everything solidly to the firewall. There are hex shaped sockets on the inner connector half, but there are no nuts in there: I don't know if they are missing or the connector never had them and just used the clips to hold it to the firewall.

should be a female side on the inside of the firewall and the male end plugs into it on the engine bay side. it plugs in snugly with the bolt to make sure it doesnt vibrate out.

Yes, I figured it out a long time ago. The clips just hold the two pieces together so it's easier to get the two little screws started into the nuts.