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That might be the bit that hurts.
weren't a lot of the dragways chrome/steel so they all rusted over time?
Personal opinion, but anything over a 16" wheel on an early Commodore makes them drive like crap....Tram tracking, rough as all guts over bumps just for starters....
So if it was me, I'd be down sizing on the diametre you're looking at
Ouch.
I reckon 15s are a good size for 1st gen.