As a Canadian, I prefer to have everything from the US shipped to me by USPS. I have had Corvette rims shipped by the post office, and they arrived just fine. Not all on the same day, but they got here. The frustrating thing with UPS or FedEx, is that there is always another cost on top of the shipping, and you never know when the bill will come, or how much it will be.
If you are selling used parts into Canada, just mark on the declaration slip that they are used parts, made in USA, and they will arrive just fine.
Thanks, John.