As far as using flexible hose over hard line............after talking with MSD, they said as long as the hose is good for over 50 PSI you can use it. I saw a hemi a guy had plumbed with braided stainless line and it was not a problem.
I was told any line that is for fuel and can handle up to and over 70PSI will work. And you only need to have the higher pressure line from the fuel pump up to the EFI. From the tank to the filter, it can be a lower pressure. I already had Aeroquip line that will handle 400PSI so I guess I am ok.The master kit comes with Aeroquip line that you can use with the push lok fittings. The push loks do not come with it tho.