Yes. The elbow is its own piece with a male end on both sides.
I think Pjam's idea is a great solution to have the proper Luke cross sabers with Vader (even if its the wrong Vader).
Again, the elbow can be pulled from the bicep or the forearm. It's a connector as well as a joint.
It's possible that old body has a different design and that the female portion is different inside -- but it shouldn't be too hard to make it work with some modification (snipping off the end or sanding it down to make it fit). People swap arms around here all the time. Open up the chest to replace the entire arm if that's what it takes.