feel fortunate! You have a relatively rare, beautiful and desirable snake. If you're interested in breeding, the opportunity to produce more of that same kind should be very appealing, though the babies will be hard to feed (this offered in the name of "full disclosure"!) as is the case for all the small milksnakes.
I'd encourage you to put in the effort and see if you can produce more. Some of us--not all--object to crossing to a different subspecies or species because you can't then revert to a truly pure animal. Having said that, if you want to try to cross it to a kingsnake, as you asked about, put it in a cage with almost any of the getula kings and that will "eliminate" the objections about crossing (I'm kidding here--the king will eat your animal, in all likelihood).
Keep in mind your scarlet "king" is actually classified one of the many milksnakes, not a kingsnake.
peace
terry