Cadillac: production date for eldorado

for legal reasons (in my stupid country) i need to know if an eldorado, 1968
model, was also available with a production date PRIOR to 1968?
was it possible to buy (including delivery) a '68 model in 1967?
would that production date up show up in the vin number?
can anyone confirm that the '67 had exposed wipers and the '68 had hidden
wipers?
i'm also looking for frame off restoration pix for this car.
did it have a separate chassis or was it unibody?