You should take a look at the casting number on the heads that are on your motor. You should either have an 862 casting or a 799. If there is an 862 casting on the motor right now then obviously you have just purchased the same thing. If it is a 799 casting it is actually and LS6 head which will flow a little better then a 862 casting will once ported. 4.8l motors don't have heads specifically made for them, the runner will be same size as on a 5.3l truck head.