Need some fuel line help!!!

[79BIG10]

Let me explain the situation. I have a dual fuel line mechanical pump on the block. The line to the return line was leaking before and I fixed it by blocking off both the pump line and the valve line. Well today coming home I smelled fuel vapor and got home to hear a PSSSSSSSTTT sounds coming from under the hood. After searching the supply line is leaking this time right under the motor mount No way to repair line so time for a new line. I'll have to remove the header and maybe the inner fender but that's about all I can take off. I'll replace the lines with one supply line and do totally away with the return line. Now here's my problems:

1. I'm going to install the new line on my first day off this week so I need to find out what the existing fuel lines are being held in by.

2. I'm thinking I'll stay with steel lines for the long run unless I should change to something else?

3. 3/8" size right?

4. I have already replaced the rubber lines so no need there. What do I need to hold the new line in place with?

5. Anything else I'm missing?