TO be honest with you there is very few info on the G63 as only 20 or so were produced..
try benzworld.org
here is some info from a BMW Site hehehe!
05.11.2002 new of the AMG g-model - immediately as AMG G 63 - V12 available Offroad classical author with 326 kW/444 HP strong AMG twelve-cylinder engine - 620 Newtonmeters torque provide for sovereigns road performances - Unikatfertigung of the Mercedes AMG manufaktur - available also as sieving or Achtsitzer with specially-long wheel base - individual ones of desires with Exterieur and Interieur are fulfilled Highest drive comfort, strength in the abundance, dynamic road performances and superior Offroad characteristics: The new Mercedes Benz G 63 AMG unites many peak values. Under the hood of the jeep classical author built since 1979 AMG twelve zylindermotor with 6258 cm a capacity, a maximum output of 326 kW/444 HP at 5500/min and a maximum torque of 620 Newtonmeters works at 4400/min. The acceleration of zero on 100 km/h completes the G 63 AMG in 6.5 seconds, the maximum speed amounts to 210 km/h (abgeregelt electronically). The world-wide only available Offroader with twelve-cylinder engine (!) developed on special customer's request and in a very exclusive number of items by the Mercedes AMG manufaktur in manual work was manufactured. Beside the fuenfsitzigen station car the G 63 AMG is available also as sieving or Achtsitzige variant with specially-long wheel base. Thus the Mercedes AMG GmbH demonstrates the rapid and flexible conversion of special auto+mobile special wishes. No borders are set to individual desires in the Interieur and Exterieur: For the G 63 AMG and all other models of the Mercedes Benz g-class are available special noble wood -, carbon and leather variants as well as different HiFi -, communication and Multimedia equipments with monitors in the head restraints. Also a glass sun roof, a separate rear air conditioning system and often electrically adjustable rear single seats for greatest possible passenger comfort can be realized in the Mercedes AMG manufaktur.