Read the fine print.
1. Vehicles built before 1 January 1989 -
Vehicles built before 1 January 1989 may be imported to Australia without restriction. An import approval is still required and the enclosed application from should be used.
The vehicle must be built prior to 1 January 1989 unless it meets the transitional arrangement below:
 If you made a financial commitment and purchased a 1989 or 1990 vehicle prior to 7 February 2005 you may apply to import your vehicle until 31 December 2005; but if the vehicle is a 1990 year of manufacture you may only apply on or after the month when the vehicle turns 15 years old, eg a vehicle manufactured in September 1990 can be applied for import in September 2005 provided there was a financial commitment before 7 February 2005.
 vehicles built during 1989 (or later) that meet the specialist and enthusiast vehicle criteria for entry will need to qualify under RAWS as meeting the Australian Design Rules that applied at the date of manufacture.
Nobody to my knowledge has spent the money to get the RAWS Certification for '89 -96 C4s therefore they can not be complianced therefore they will not issuse an import licence.
See
www.dotars.gov.au/transreg/str_sevs.htm John Bondok in Bris had to send his unconverted '90 that has been in the country for several years to NZ and back just to get the right paperwork to allow him to convert it,
Import paperwork incorrect =no rego.
I believe Corvette Alterations & Conversions in Dee Why don't do C4 conversions , mainly C3 work
