I guess it is possible that a few "grey" market Kadett C's made it over, but unless it was a GT/E (which had the 1.9 CIH, only 10,894 made), most were either the 1.0/1.2 litre OHV or the 1.6 CIH engines, which sound a bit too basic to have the big brakes found in the later Manta. But I really dont know and I am just speculating
Hmmm, you probably found one of the highly desireable Buick/Opel Isuzus. Basically a Kadett C made in Japan. It used Isuzu running gear and aside from the fastback body style, it was pretty much a Chevette, which was a different Kadett C body style, but used the Isuzu motor. If this is the case, then it will not have the 75 and later Manta brakes.
Yep, I'm pretty sure that's an Isuzu. German Engineering gone bad over in the land of the rising sun. I don't believe that much of it is compatible with the German Opels. Here is what a Kadett C GT/E looks like. Pretty similar bodies, but as opelbits has stated, completely different running gear. As I understand it, some of the basic designs are similar, but applied somewhat differently. Hmmm.... It might be interesting to pull some of the parts (such as the brake calipers and rotors) and see just how different they are. I believe that they used a 4 x 100 mm bolt pattern, but I suspect that they used NipponDenso brake gear rather than ATE (Alfred Teves) brake calipers and such.
The fun things to do would be to see if:
1-short of importing an entire Kadett C GTE, take an Opel/Isuzu and install Opel front shetmetal and one of Bob's 2.4s with a Getrag. A do it yourself Kadett C with ooomph!
2-See just how much of the later Isuzu Impulse 2.0 Turbo will bolt into the Opel/Isuzu I-Mark chassis.
I always did like the Opel/Isuzu. Later ones came with the 2.0 instead of the 1800 motor and there was a diesel avaliable, too.
I think you will find the rotors and calipers (shared with the Chevette, I think, to be possibly smaller than the 69-74 Opel stuff.