You can convert a DKJR or DK3 into DK. DK & DKJR are basically the same except for board set and art.
You just change board and art,(CPO,bezel,etc.) and your good to go,assuming you are using a 2 board set.
Converting DK3 is the same process except it uses the edge connector instead of individual board connectors.
The DK3 harness will work for DK. Hope this helps.
Jim