I actually did a bit of research on that topic awhile ago while I was trying to sell a car. This is a bit of information geared more towards the seller but it might give you an idea.
The Vehicle must be taken to a canadian dealership with the name and address of the buyer so they can perform tests on it. These tests are so the seller can recieve a certificate that enables them to sell it into the states.
Cost(Aprox 100-150$CDN) Duty in the amount of 2.5% of the selling price or the book value, which ever is highest.
SURPRISE! Cost=2.5% of the vehicle's value I think there may be a third item but i'm not sure, this information was given to me by cutoms at the houlton, me border.
The bottom line is...I doubt the seller will pay for these things so the expenses will come out of your pocket most likely. So you'll have to spend a little extra, but if it's a good car I say go for it! Just remember, you might be stuck with a bill

for the certificate tests only to find out the thing can't be sold into the states

.
Hope it's a help, good luck on getting an SVT
Alec