Actually.....
Actually, if you are set up to do that - it is.
My experience was as follows:
Show up, tell the officer what you've got. Airplane parts are NAFTA so no duty. You will get picked out, go to the office show the invoice to establish the value, swipe your credit card for the sales tax and be on your way.
As always when you drive across, if they want to, they can look at closely as they want, which is the YMMV.
Derek