could have sworn i posted this before...
I have three mk1's in my driveway all with screw-on speedo cables.All German built (obviously as all mk1 Jetta's were), one is a 1981 1.6D, the other two are 1984 1.7 EN gas cars. All three were screw in, all three with factory installed clusters. I think you are mixing Rabbit facts in with Jetta facts. All mk1 jetta's (1980-1984) are all the same dash wise.
now kilo speedo... educate me...