72 Duster340 universal joint question.

[reno340]

I have a 72 Duster 340 w/ 727 auto and 8 3/4 rear. I was looking to get a set of universal joints for it (front and rear of drive shaft). In looking to order them, I have a choice of 2 sizes. (1) 1.078 Inch Bearing Cups (2) 1.126 Inch Bearing Cups. How do I tell which size I need before I order them?

 

[jar84203]

Take the old ones out and measure them.