I noticed between the 2 different one's the cam phasers and chains are different, I had a vz sv6 ute I got cheap and went to replace the engine with an earlier model from a Calais all it did was pop and fat when trying to start. A mate that knows more then me said unplug all the cam sensors all 4 and try start it, the fucker ran strait away!
So to get it going pulled cam phasers and gears off and old one at my brothers install newer timing chain kit then she ran perfect on that motor.
Seems to be chains and gears between models