Superbird park brake cable.

[Plumpcars]

I'm trying to track down a long rear park brake cable for my Superbird. It has stock front discs/10" drum rear. I find cables and kits that say for all 68-70 B bodies but according to my book the right rear on 70 Roadrunners with 10" drums is different to previous years. I checked the advertised length on a Dorman C92321 (Listed for B body but NOT 1970 Plymouth) and it seems the same as mine. My confusion is why do some kits say all B bodies but the book and Dorman  tell me that 1970 Plymouth is different? I'm in the UK so buying parts tends to be harder for us. Thank you.

PS: One thing I have noticed is that the part number for the short brake cable remains the same for 1970 as the earlier B bodies.