My shock looks like this and yours should too:
http://www.ebay.com/itm/2007-09-Che...Parts_Accessories&hash=item334c05436f&vxp=mtr
The unfinished metal circular parts lowers on to the bulge from the top of the strut, and then holds the lower perch seat. There is no groove on my shock what so ever. There is none on your shock out side the one you made either.
My stock, Bilstein, and Belltech struts all look like the one pictured above.
When the lower perch is lifted, one will see the metal perch holder pictured above. When that it lifted, one will see the bulge in the shock that holds it on.
So unless your mods involves the use of snap rings, there are no snap rings on the shock.
---------- Post added at 08:18 PM ---------- Previous post was at 08:17 PM ----------
Let me go take a picture of my stock front shocks and upload them. I will be back by 10.