When I swapped my drums for discs, I used '72 spindles and brakes. I had a real problem with the lines. The '70 lines were different than the '72.
Sorry, but, don't remember what was different. Was 3 years ago.
I am useing the stndard brake booster, instead of the power booster.I used the '70 master cylinder. The lines worked with the '72 disc prop. valve with no problem.
Where I ran into trouble was at the calipers and the rubber hoses. They were a different size than the '70 hoses, but, that is all I can remember.
I know this is kind of vague, but, all I can remember. Hope this helps
If you are going to be dumb, you got to be tough.
'70 Mustang Fastback,460 powered