[GTJIM]

It is the steering arms that are different - I am guessing Opel did that for a good reason ...

Maybe someone can tell us if the GT and Kadett racks interchange - or do they have different angles on the pinion shaft?

Just had a look at the Parts Book: The rack housings have the same part number for 1969-73 GTs and 1968-72 Kadetts but GTs have two different gear sets (1969-70 and 1971-73) and Kadetts three different ones including a seperate set for 1.1L.
Be interesting to know exactly what the differences are ....

I know the later Kadett (1968-72) inner and outer ball ends are the same as the GT ones. The earlier Kadett ones (pre-1967) are lighter and have different tapers where they go into the steering arms - there were several changes in front suspensions in 1965-67 and all the parts do not interchange.