Don't tell them it's a used car part and then show them a shiny header. They've heard it all. I've seen them look things up online to find their value. They can flag you to be checked every time for 7 years if they think you've lied to them.
Duty will vary depending on the country they're made in.
I've used
www.usaddressinc.com for about 15 years. Just across the Queenston/Lewiston bridge. I've also had large things sent Fedex freight or ABF freight and picked them up at their respective terminals in Buffalo.