It is my understanding, that the transfer case on both QDII and QTII is exaclty the same. As it is the same part number.
Also, differential brake control activates its function when one wheel is spinning faster then the other on the same axle. In theory, once they are manually locked the computer will never know the difference, as both wheels will be spinning at the same speed.
Regarding the aftermarket locker, The best would be an ARB locker, but that is $1,200(locker,Air compressor) + labor. An Auto locker, is much cheaper at $350+/-... but it has its handling quirks, and that is only for the rear.
My option would be close to $600, that is for both axles, with manually activated lockers. Labor should be much simpler as they are suppose to bolt on.
2005 Jeep GC Limited 4.7 QTII
2.3" RRO lift Bilstein Struts/Shocks 255/70R17 Cooper AT3