Hi,
Took me awhile to find the correct URL. The breakdown you gave is all-well-and-good and I have used that site here, and about half a dozen others. It does not show the electric clutch.
From what I can tell the tensioning mechanism must be changed for the primary belt. Most of what is on the tractor with the 42" ought to work. Just taking a couple of moments glance showed the idlers and some other pieces should swap; did not check spring or belt, and there is a difference spring-wise as manual uses two and electric uses one.
This owner's manual is far better as it shows both manual and electric versions:
http://manuals.mtdproducts.com/mtd/D...770-10130e.pdf
Peace,
Clarke