As long as you have an MSO/MCO and the VIN is on the car somewhere that you can point out to the person verifying it you shouldn't have a problem with Oregon registration. Since it's an SPF you should be o.k. on the VIN plate. Took me about 20 minutes to register my new ERA when I got it.
I took delivery of my car in Denver (turn-key ERA) and had two days to "shake it down" before my trip back home. Very close check for leaks and drips whenever I stopped on those two days before I hit the road. 1300 miles total Denver to Portland. Only 150 miles the first day but I had made advance arrangements to have the
oil and filter changed at that point just to make sure things were still o.k. Cut the filter when it came out and took a really close look at the element and the
oil in the can. From that point on it was a close check any time I stopped for gas or any other reason and all went well.
If you aren't planning on spending at least a day on shake down I think I'd recommend having at least a chase car trailing you on the trip back down to PDX just for peace of mind. I'd also recommend the
oil change and cut filter when you get home. No reason to think that there'd be anything wrong but it can't hurt and it's better to catch any problems early on.
What part of Oregon do you live in? As Bob mentioned earlier there are a couple of groups here that you may want to touch base with. Probably the most active is Cascade Cobras out of Portland and southwest Washington. If you live in the northern part of the state it would be a good place to start. Several Superformance, a few ERA's, a newly arrive RCR GT40 with various and sundry other manufacturers. The lion's share of the cars are FFR's so you've got a reasonably broad representation or producers. Just getting into the "season" so there are a number of activities scheduled if you're in our neighborhood.
Good luck with the new toy.
DonC