coupler/rag joint??

[LOW DOUGH]

I have two questions about this coupler/rag joint.

1. What is that wire in the center for? I see it connects a bolt and a pin, but why?

2. Are there two different size couplers for the 2wd, w/ power steering?

I am putting a 69 tilt in a 71 that had manual and I switched it over to power long ago. I used a gear box from a junk yard truck. I don't know what year it was, but it was a 67 -72.. I have two different sizes????

Maybe I can clean it up tomorrow so I can get a better pic....