try this untested ,
bomb = "Bo_GBU12_lgb" createvehicle ( truckplayer modeltoworld [0,0,4])
i presume your truck is named truckplayer in editor ?
adjust the first zero , positive number for west , negative for east
adjust the first zero , positive number for south , negative for north
adjust the 4 for more height
this wont change the blast height , for that you will need to collide your bomb with another object before it hist the truck .i am sure mandoble made a thread about that many moons ago.
good luck
DB