I bought the kit for two door cars that has two 5 wire solenoids and a control module. The solenoids are push pull so they need to be mounted below the door lock rod so it can pull and push straight. The perfect mounting location is right where the large hole in the door is so you need to make a mounting plate. I made this plate from pretty thick aluminum, but a fairly stiff piece of sheet metal (steel) would work fine .
The kits come with a push rod and a coupler that has several set screws and is designed so you can simply lay the new rod parallel to your existing push rod and tighten the set screws on the rods to hold them together. The set up worked fine on my Toyota pickup, however; it will not work on the Opel for several reasons. First the key mechanism is inside the door handle's push button so everything is internal to the mechanism so you can not connect to the key side of the lock. You have to use the manual knob that protrudes from the top of the door on the inside. This rod is much smaller than what I had on the Toyota and much smaller than the rod that comes with the power door lock kit. Because of the size difference the coupler does not grasp the thinner rod that well, and would most likely come loose if you could get it to grab at all. In addition since that rod is on top and you have to mount the solenoid on bottom it looks like it will conflict with the operation of the mechanisim.
Finaly since the door is real thin at the top there is not enough room to get tools up there to attach the coupler.
Because of this I decided to fabricate a longer arm for both of the rods to connect to and attach it to where the original rod connected to the original arm.
If I was to make these arm extensions again, I would make them longer and instead of having the two rods above and below each other, I would attach the original rod inboard and the solenoid outboard. This would give the solenoid more travel (which it seems to want) and it would also give it more leverage to overcome the spring. The spring I am talking about is designed so that when you pull the lock knob up it is sprung up and when you push it down it is sprung down. This spring is pretty strong and yet is not needed with the electric, as the solenoid will perform this function quite well. Because the spring is so strong I had problems with the solenoids not having enough power so I had to squeeze the spring with a pair of needle nose plyers to get rid of some of the tension. Don't even think of doing this without taking the door handle and mechanism off. It is not that hard and it gives you a chance to clean thirty years of crud out of the mechanism and lube it up again.
This picture shows the arm extension. I simply attached it with a single pop rivet through the hole that the original rod connected to. In order to keep it from rotating with the single rivet, I made a notch in the aluminum that fit the arm like an open end wrench. This left two ears that protrude on either side of the original arm where it makes the bend and keeps everything solid.
Once this was installed I had a minor conflict with the rod that opens the door from inside the car. Since this rod runs forward from the mechanism to the inside door handle, it crosses the solenoid rod and they would rub and make noise so I took and made a V bend in the rod so it would clear. You can see it in the previous photo and in this one.
The last step is to get the wires into the car. The wires exit the door just below the upper hinge and are protected by a spiral wire wrap and then zip tied to the bottom of the hinge. Then you need to file the slot in the fender that the hinge retracts into when it closes so that it does not cut the wires when you close the door. I filed it down quite a bit and then covered it with a slit open piece of vacuum hose glued on top to further protect and give a finished look. You should be able to see the black hose in the picture just below the hinge. The wires then leave a small loop and enter the car through the original dome light switch wire opening. If I remember correctly it is a hugh hole with a very large grommet already. The bundle in the photo has seven wires wrapped in plastic spiral wire loom( two for the blinker in my mirors, and five for the door locks)
Hope this helps.
I later installed an alarm with a remote and trigger the locks from that. You can get kits that include the remote if you don't want the alarm.