j, thanks for the link. I figured it would come to that. I'm gonna give Cimarron a call tomorrow. It looks like the main internal departure from an original SAA is a coil hand spring. However, this appears to be part of Cimarrons "Cowboy Comp action" That all Model P's have. So that part is not unique to the ER model. That said, there are at least 4 different hand springs (two flat and two coil) listed in the parts diagram.
In the end I'm just trying to stay as true to the original as I can so I may just go with an "old model" P and send it to LongHunter to slick up.