i imported a 1981 porsche into canada in 2009 (over 25 years old). i can't find the paperwork but i think i paid 6% duty IIRC (plus the $100 a/c levy).
just an FYI, i found two sites that are pretty helpful about importing a car into canada. the first site deals with importing a car into ontario (generally), and the second site deals with importing a
kit car
How to Import Car to Canada? , Importing US vehicle to Canada.
"Kit Cars" in Canada - Transport Canada
Frequently asked questions for Kit Cars - Transport Canada
the Transport Canada FAQ on importing a kit car is pretty interesting and easy to read. must have been written by a 'car guy'