You need to verify with the contractor that the turns ratio, phase shift and impedances will be properly matched. Then run the calculations based on the numbers provided to see what the circulating current would be.
As mentioned above, you need to check the winding pitch on the alternators to ensure that they match. Most likely, considering you are getting 2000A of circulating current, they do not match. I would look at "Power Systems Analysis" by Arthur Bergen pages 125 thru 127 which discusses...