Bringing 2 vans (donor van to fix the other) into the United States

I have a rare JDM campervan with a broken CVT transmission I can't find a replacement for. I've bought a manual transmission donor van intending to do an engine+transmission swap.

The van is in Vancouver and so will the donor. Problem is I live in Ontario so have no space or tools or anything to do this job. There are no community DIY garages like they have in the US where I also have a friend that will help me on the project. So I want to stick one in a UHaul truck and tow the other behind it down to Seattle.

What the heck do I do about the donor van I plan to scrap/part-out for backup parts? Do I import in BC, register+plate it then take it as a personal vehicle? Do I leave it unregistered? Do I get it shipped to Seattle and imported as an American vehicle?