You'd be better off looking for Kadett C parts, which of course, weren't sold here.
The Kadett C, Opel-Isuzu I-Mark, Vauxhall Chevette, and US Chevette were all GM T-Cars and are very close platform wise.
Here's a thread you might want to look at:
Grassroots Motorsports and Classic Motorsports / Chevette
You can put in a GM T5, as well as an S10 rear axle with available LSDs and Ring and Pinions.
Kits are out there to put in a Buick V6 or the Camaro narrow angle V6.
Springs are pretty much universal, as the axle cups/links are the same as on the Opel, all three link with Torque tube. Bilsteins available.
If you look at the classifieds section, I have a set of flares similar to those shown on the Vauxhall on the above thread (actually meant for a Kadett C), but no front air dam.
Regards,
Wilson
PS: Also check out
The Chevette Photo Gallery