Dave:
I used the Chevy parking brake cables on my GMC. The way I did it was to cut a slit on the brackets that hold the cables and slip the Chevy cable into the GMC bracket. Alternatively, you could inlinetube.com make up cables to match yours. I used them to make the intermediate cable to my specifications because the length of it was a bit off due to the Chevy cables on the backing plates.
I hope this is helpful. I think what you have is workable rather than trying to change backing plates.
Regards,
Steve
New Orleans.
