I haven't really looked into it, but at first glance, it appears to me that they have replaced the rubber middle with two steel angle pieces. I may be wrong, but I think the only change necessary is to drill a new hole on each side and bolt on the new cutting edge center. If this is true, you will probable have to replace your main cutting edge as they would be shorter (you could probably just cut your originals, if there not too worn).
Again, this could be way off base, but, on the other hand, I may be correct...LOL. Hopefully, someone will come on here and set it straight.
You can take a look at the instructions to install the new 4 piece cutting edge here: http://www.westernplows.com/pdf/29665.00_031507.pdf
It looks like it's a pretty good possibility.