struggling with connecting the wiper rod...pics!

It sounds like you are trying to put a square peg in a round hole...
I had a similar problem when I was putting my '72 together. I ended up getting different linkage arms from a later car. I couldn't find any of the plastic bushings without the tab on them. That tab goes into a slot on the linkage arm.
I am not sure what was meant by the studs being straight with a groove in them, mine had a ball end which went into that plastic bushing.
C