Been ages since i posted, never got time etc..
This may have been already discoverd previously by somebody else who's fed up with the ancient headlamp adjusters that crumble as soon as you breath on them.
Anyway, By chance i had an old 2004 Toyota yaris in for repairs to the front end, had to change both headlampas with cheapo DEPO versions.
Yep.. the plastic adjusters are an identical fit to ours, even the black, rubber o-ring is exactly the same..
Unscrew the DEPO's adjuster (DEPO or Toyoyta manual adjusted headlamps only, electric motor versions obviously have electric motors without the adjuster needed)
First put your corrado's adjuster in a vice and remove the adjuster's plastic thumb wheel by pulling it (carefully) off, screw into the new adjuster your old 'raddo threaded adjuster and press back on the thumb wheel and refit your new adjuster in the corrado's headlamp and adjust the beam.
No more searching for expensive, 30 year old bits of shiyte plastic..
P/N on the DEPO's adjuster: 32-212-11A4N2 or 32-772-1101N3.
I've got a few photos but i can never seem to upload them here..