More Brake Questions

[one9six9]

Okay, I have been reading this forum, but don't have quite all the answers I am looking for.
I have a 69 with manual drum/drum brakes. I have aquired a crossmember and rearend out of 72 so I can do the disc/drum conversion. My questions are as follows:

1. Can I use any booster and master cyclinder from 67-72 as long as I use the correct proportional valve?
2. I will need to replace the front brakelines from the master cylinder to the front calipers and to the front to rear line. Can I use any 67-72 brake lines or do I need to use 71-72 brakelines. Is there a difference?
3. Am I better off just replacing all brakelines, or can I use the brakeline on the rear axle.
4. I read on another post something about the lever being the correct lenght for the brake booster. How do I know what length I need?

I'm sure there are other questions, but I can't think of them now.

Keith