Putting in an 8 3/4 rear in my duster that has a 7 1/4 rear parking brake cable question.

You all can think what you want. There is no way a cable for 9 inch brakes is the same as 10 inch brakes. I have them here and the inner cable is shorter for 9 inch. even the spring on the cable is a different length.
Did the same with my 73.
In 73 your 7 1/4 could have had 10 inch brakes. Most 73's didn't come with 9 inch brakes. Also 72 and newer took the same cable for both sides. I have installed many 8 3/4's and when ever the car had 9 inch brakes the cables needed to be changed due to the cable being shorter including the spring in the drum. Could you rig it to make them work? I don't think so how would you lengthen the spring and cable.

I'll get you some pictures of the two cables side by side if you all need them. But common sense should wake your brains up.