I have a spring assist top on my JKU. It has brackets that are bolted to the roll bar in the same place your 2012 brackets are but are shaped different. The spring assist part is built into the tops frame so unless you change out the frame I don't think you can add the spring assist to a 2012 or older top. You could look around and see if you can find a 2013 top and swap the tops. Then you could sell your to get some of your money back. I got my top off ebay for $700 so they are around.
2013 Jeep JKU Sport S white auto 3.73, lifted on 35's
1997 Jeep TJ Green 2.5L, 5-Speed, lifted on 33's
2003 Jeep TJ Silver 4.0L, Auto, Stock so far