I didn't realize that there were two different flanges that bolted to the differential output shaft for the R180.  I had only encountered the 70-73 flange that used 4 bolts to bolt to the output shaft as shown in Zcarnut part diagram.  The one that the PO installed in my 1971 is the 74+ that the flange bolts directly to the diff.  

 

Thanks for the clarification, I didn't know there was a change beginning in 74.

 

 

 

So you're saying that there's a bolt head under there?

From that diagram it would appear that way.  I didn't see it from from the angle and dirt in the area.  When I get a chance to get back under the car this weekend, if there isn't one, I'll post back, but otherwise assume I was ignorant of the different design in the 74+ versus the 70-73 that I have spent more time looking at and researching.  

There's a bolt that goes through the shaft and into the diff. You can access it through the gaps in the u-joint area.

 

Chuck

I took a couple pics tonight of some of my halfshafts. You can see how the bolt passes through.

 

 

 

Chuck