Thanks that's what I thought, this is my sons car, he is on a bit of a budget so I think we will stay with the 73 one as there only about $50.00 but just out of curiosity why do some members here like the newer style ones?,
In general, you should be matching your master cylinder bore to the bore size of your calipers.
Since you are using a 73 disc setup, I would go with the 73 MC.
The newer MC is aluminum, making it lighter. The bore size is more than likely different as well.I have one in one of my Darts, and notice no difference in braking.