Hi Jep,
Right don't cut the connector off at all.
Compare the positions of the wires in the connector that came with the clocks that you want to fit, with the existing connector already on the car, these need to match, so is a simple case of opening the rear of the connector block on the cars connector, and using a very small jewelers type screwdriver prise out any pins that don't match and move them around as necessary, till they match the connector that came with the clocks.
This will most likely leave you without a green wire, if so note the position of the green wire in the connector that came with the clocks, and remove this wire, and put it in the same position in the cars connector, it then leaves you with just one connection to make between the cut green wire now in the cars clock set and the negative - of the ignition coil to get the rev counter to work.
You will see when looking really carefully that you can prise the rear of the connector off, it is a hinged lid, then you will see a tiny square hole in the front/clock side of the connector, putting a pin, jewelers screwdriver etc in here will push back the sprung tab holding the terminals in the connector block, then easy to move around.
tabetha