I did the reverse. The drive train from an Opel GT was basically the same as for the Kadet. One day my rear end gave out. The american version of the Opel GT did not have a rear anti-sway bar but had nylon plugs in the bold holes for one in the frame. I bought a rear axle off a Kadet in the junk yard WITH anti-sway bar. Really improved the handling.
I knew where all six Opel GT’s were in the Seattle junk yards.
And that brings up another point: Until the mid 1980’s I spent a lot of time in junk yards. I’ve not been in one for decades.
My Kadet was an automatic which burned out. It got 19 mpg. I noticed extra brackets under the dash so I went to the junkyard and got a GT 4 speed and bell housing and clutch pedal. I had to drill and tap a few holes in the bell housing but it was a Saturday chore to convert it. I also got the fancy wood steering wheel and shift knob. After that it got 33 mpg and I used it several years.