There is no way you need them that long. I have lines that are pretty dang long but nowhere near that long, they worked in my blazer and it flexed more than any 56" spring or 52" spring I have ever seen. Mine were never even close to tight and I think they are like 30" or something ridiculous like that
You need to flex it I am sure you don't need them that long. I bet most guys here are using off the shelf brake lines.
I helped build Horton (my current truggy) and when we went looking for brake lines we looked in a catalog at a parts store and found a stock application that would work, I think they were 25" long, I don't think they ever got tight either.
I only swapped on the longer brake lines cause thats what I had when I put my axles under Horton