Cmdcntr,
LemonJello,
the new 1/48 CH-53 GS/G is the best starting point. The old Revell 1/48 CH-53 doesn't have the correct rotor blades. Cobra Company (exterior) and Cutting Edge (Cockpit and Weapons) have all you need to convert the Revell 1/48 CH-53 to a MH-53J Pave Low III.
Converting the Revell kit to a USMC CH-53E is rather hard. The Echo differs in many ways (other rotor head, longer tail section, different tail rotor etc.) to the Delta that is still in service with some USMC units. So if you want a current USMC CH-53 you could go the easy way and build a CH-53D from the Revell kit. A CH-53E is way more work but not impossible. Just remember that you will not be able to use to much of the Revell kit.
There is a nice 1/48 CH-53E in the Gallery over on Heli Kit News. It looks like the Revell kit converted (scratchbuilt) to the Echo. Very nice job.
HTH