The first issue that I see is your first host the ML370G4 that is a very old box and is not on the HCL for the latest versions or ESXi. also it only has 100MB network cards and at 4GB memory it would be next to useless for as a Virtualisation host. also I am not 100% sure but I do not think that you can run 64bit guest on that model as their is not VT extensions on the BIOS.
Also my earlier discussion regarding EVC will not help you here as the chipset in the ML370 is too old.
I would concentrate on the second host, and upgrade its memory, this will allow you to run more guests.
the upshot is with your hardware as it stands you will not be able to create a cluster. as the models are too far apart.