579724-03 = replacement for 396505-20 = 12v motor
579724-04 = replacement for 396505-21 = 14.4v motor
579724-05 = replacement for 396505-20 = 18v motor
brushes part 603754-01
brushes fit all 3 the above motors. the stock esc will run the 12 & 14.4v motor. the 18v motor will run but undervolted, buy a mamba monster instead.
The 12 volt motor is 1650kv, 14.4 volt motor is 1350kv and the 18 volt is 1100kv.
theres a few sources for these motors,
also you can talk to your local dewalt or black and decker power tool parts suppliers and buy it thru them.but be prepared to take a loan to afford to buy it thru them.
some good info here
plenty of good info here on the traxxas forums too
hope this helps someone