I just bought a 04 Pacifica and found out the rocker arm assembly needs replaced. lifters have failed. Can some please explain to me why every other 3.5l lifters can be replaced instead of replacing the whole rocker assembly except for the 04 Pacifica with the vin # 4. I have found the replacement lifters for the 300, 300m, charger and Sebring ,but none for the 3.5l in the Pacifica.