We are full timers with SD as our domicile state. That said, if you're a SD resident the DMV has nothing to do with your situation. All vehicle transactions are handled through the Tax assessor's office.
We purchased our toad in Alabama last year from a dealer. Paid cash for the car, paid zero dollars to Alabama. Dealer gave us a temp plate and we took care of getting it registered in SD. Kept the same plates off our old car and put them on the new one. Everything was done on line except for the amount due. That was done with a phone call to the tax office. They will need either a bill of sale or the dealer's contract agreement. Copies are ok. All this is on line on SD website or you can contact your county's tax assessor.
If you're not a full timer and/or a SD resident, then none of the above applies...Dennis
If you have Americas Mailbox as your mail forwarder, call them with the purchase info and they will do it for you...D
HERE is the form you need to fill out. Print it and take it with you to the dealer where you're purchasing the vehicle.