the dry sump system thats on the LS7 doesnt use an external oil pump, the oil pump is still in the motor.
as far as the differences between a 3 stage pump and a 5 stage pump...the numbers refer to how many ports the pump has to feed back into the engine. with a 3 stage pump, you'll be able to run 3 seperate oil lines to the motor, with a 5 stage pump you can run 5 lines. at least that is my understanding of it
