Jan:
Might want to try an appeal to CT Emissions, contacts are:
http://www.ctemissions.com/contact.html
Looks like a Catch 22 situation. As a Composite, the emission standards would be those in effect in the 60's & 70's, not 1998.
Could be just an Administrative situation with CT Emissions, if the DMV recognizes the vehicle and year, then the appropiate emissions standards should be available. Maybe their database was not updated due to the rarity of the auto.
Did you ask why the default is to 1988 ?