Apparently, you can use their address as a physical address. It caters to rv'ers. You can get South Dakota plates, license, even register to vote. I've looked into it a bit, seems to be in conformity with SD law. I had Progressive do a quote; I would save over $800 by doing this.
Wife and I used a service like this out of Sioux Falls .... Was great but you have to make the trek up there once if you want to move you drivers license too ! It was called "your best address " great people
I hear good things about them, as well as the one I posted about. One trip to SD wouldn't hurt, IMHO; there's touristy stuff up there. Tags on the van would be $130, vs $153 in PA. No property tax either state. Also, SD doesn't have state income tax
I did something simular for licensing puposes but the house I stay in borders east and west of Missouri river. Licensing there is cheaper but I also like the small town folks as well