I have a bulkhead from a GEN II 600 RMK in my garage. The cooler part is not the problem, its the motor mounts. The fan sleds have a different mounting pattern in the bulkhead, a lot different actually. The 550 motor has a motor plate mounted to it which mounts to the chassis via the motor mount bolts in the chassis. The liquid sleds have motor straps that mount in different places of the bulkhead. The mounting pattern on the 550 cases does not allow me to use the liquid motor straps either. So, unfortunately without heavy modification a liquid GEN II bulkhead will not work. Thanks though.