Hey Kevin,
If you import the LSD diff and bits from outside North America you'll end up paying the duty. Using a bonded carrier like FedEx may get your parts in more easily, don't know for sure. However, if you ask nicely from your LSD source to write (and you didn't hear it form me) the bill of sale for say $150.00US that will reduce the duty rate. I know MDA has LSD options for the UN1 you may be able to purchase off the shelf but due to the nature of these transaxles becoming way of the Dodo bird, it may be more difficult to find for a fair price. (I like the Dodo by the way, poor little bugger never hurt anyone).
Chris