Hi Chris,
I have a mate with a rebuilt ’89-'90 Walkinshaw Commodore, recently refitted with a reworked later model V8 & trans. It now has a major speedometer error and I don’t think that model has a diagnostics fitting? Can you recommend someone who can recalibrate speedos? When you changed my Z28 from LT to LS we had the same issue (not helped by increased mag size from 17” to 19”). I recall you had a guy in Blacktown or St Marys with a dyno that adjusted speedos?
Cheers, Bob.