Paul,
You may or may not be aware that the E1 and E1e heads are completely different. I have modded E1 heads to be made LE compatible, but I don't think it's worth it. You have to "tiptoe" around the clip fastener hole, the lens is invariably screwed up in the removal process and you can only use the stock reflector which, IMO, sucks. Consequently, I'm not doing the mod on the E1 or E2 heads any longer.
The E2e head is another story. You can bored it out to accept a modified McR20 reflector and chase the threads to accept the light engine of your choice. This is a nice mod. It results in a just about the smallest light possible that has the kind of output that you get.
From a cost perspective, you could just go with an Aleph head if you don't mind the light being a bit longer, because the costs are about the same.
If you're interested in the EXe head mod, get in touch with me. If you want an Aleph head built, there are a few differnt people that you could contact. Check out the McGizmo forum.