Brake line question

[coupe5.0]

I'm getting ready to order the stainless brake line kit for my car, and after looking at the catalog have a (probaby dumb) question. There are different kits for 28 and 31 spline rears. My car is a J-code 302 GT car, so i assume that it is 28 spline?

What would the difference in the brake lines be?

 

[fasttback]

Unless it was changed, it should be 28 spline. I believe the high performance big blocks came with the 31 spline back in the day.

Since both axles can share the same housing I can only see a difference in the size of backing plates/wheel cylinder.