I've built the Italeri CH-53E, but without any PE parts. I can help you out in saying that the MH-53E differs from the the CH-53E in 3 major ways.
1. The MH-53E has rear view mirrors hanging off the nose of the aircraft. They are angled down and aft for the pilot to observe the sonar sled while it's being towed through the water. You can ommit rear view mirror parts on the CH-53E.
2. The MH-53E has enlarged sponsons for more fuel. Pulling a sonar sled through the water used alot of power and alot of fuel.
3. The MH-53E has a sonar sled which is stowed in the cabin while not in use. This can be ommitted on a CH-53E.
It's good to know that Eduard has made aftermarket details for Italeri's CH-53E. The kit is good, but lacks detail. I'd say that the area most deserving of improvement is the main rotor head. A 53's Main rotor head has wire harnesses and hydraulic line criss crossing it the blade roots.
If I may suggest that you use the HMH-464 decals. 464 is the best helicopter squadron in the world, but I'm a little biased. I have some reference and build pics on my photobucket site
http://smg.photobucket.com/albums/v491/ridleusmc/
Semper Fi,
Chris