Yes the rear nut/cap can be removed. If you have a belt sander ,grinder , or hand files (the LONG way to do it).
Look at it straight on from the back end and you can see how the tang has been "hammered" down.
Remove that and the end cap screws off.
Once you finish your project you will either have to use lock tight (or something) when you put the end cap back on or tighten it with a wrench and have to do every so often after that,
Just remember keep the leather washers in the same order as you took them off or, it will look like crap when you put it back together.
TAKE YOUR TIME ! Godd luck. Post a before and after pic. when you're finished.