Hi chondro48,
The most realistic CATs available are the 6 from GMAC, but retaking a CAT that you've already taken is NOT a realistic way to assess your skills. Seeing even a few 'repeat' questions can 'throw off' the Scoring Algorithm and artificially improve your pacing, energy levels, fatigue, etc. to a point that the results might not be accurate. Thankfully, the CATs from Kaplan,
MGMAT and Veritas are all 'close enough' to the real thing that they will provide you with a relatively realistic score assessment (assuming that you use the CAT correctly).
If you're trying to improve on this 720/Q49, then you have to be really detail-oriented about what you are working on to improve - and that includes taking your practice CATs/mocks in as realistic a fashion as possible.
GMAT assassins aren't born, they're made,
Rich