I just finished new floors & frames in my 68 coupe, I hooked up the parking brake cable & it touches the floor under the rear seat area. I mounted the rear brackets to the rear frame in the same place as original. Is this the way it is supposed to be? I have read on other cars to lube the cable where it rubs on the floor. Thanks in advance for your help.

 

Mine rubs the floor. There is actually a notch from it rubbing all these years.

One of the first things I learned about Mustangs is that they are incredibly cheap cars.

 

+1, Mustangs weren't first being able to priced at less than $1 per pound by being luxury. But luckily the "cheaper" cars from back then are way nicer than the "cheap" cars sold today

But yes, it should be normal for the parking brake cable to rub on the floor provided that it is tight. I'm not sure if it is necessary to lube them though, but it obviously won't hurt

 

Mine did that too.