Sounds slightly mad, but giving you already have a set of Shivers in use as well as this set then that's even more reason to keep them even just for the spares which will becoming increasingly rare with the passage of time. If only I'd applied the same logic with Hope C2's I wouldn't be in my current predicament!
I wouldn't stress about parts too much, the likes if UK Bike store have a good stock of parts, even for older forks. Marzocchi for all their faults at least try to continue to support the old (good) forks.