Kadett "A" types are now few and far between - there are not even many "B"s about as most were inexpensive wee cars that just got driven till they rusted away or wore out. The small OHV pushrod motor they have was made for many years though - right through from the 1.0 Litre motor in your 1964 Kadett up till the late 1980's as 1.2 Litre versions in Opel Corsa's and Nova's in Europe. There are still parts about but they take a bit more hunting for than parts for GTs or 1.9 Litre motors. I have a 1967 Kadett "B" and Rodney (
Killer Texas GT) has been most helpful in finding hard to get parts from his contacts in Europe.
Here is a link to a recent thread to give you some idea how nice a restored one can be (not mine - unfortunately!) :
http://www.opelgt.com/forums/general...ghlight=Kadett