Short version- I grabbed a random lower tang from the box o" parts Jake and I bought at Tulsa a year ago. Since the 4 bare receivers in said box were all lowwalls I figured all tangs were too. Imagine my surprise when I slid it into a lowwall parts gun(another Tulsa buy) and it was lower than the bottom of the receiver by 3/32".
I had always heard lower tangs were infinitely interchangeable, (think serial number confusion) so the burning question is whether low and highwall tangs are different? 
Point of interest- one of the receivers was from a Winder musket. Could this tang belong to that one? 
Thanks, Richard

I believe the tangs were ground to actions which is why it is hard to get a good fit. Many come close. It is one part that almost always shows that it docent belong with the action it's on when putting a parts gun together. I have had a few that fit perfectly but most of the time you can feel the tang either a bit high or low.
Cheer,
Laurie