I realize this is an older thread, but I figure I'll add to it anyway, in case someone is searching for info. I recently tackled this job on my truck, and ordered stainless steel transmission cooler lines from Inline Tube for $75, plus about another $20 for shipping. My order arrived fairly quickly. Quality was very good. You have to do a little un-bending from shipping, but I managed to do that without worrying about kinking the lines.
The original lines had been replaced by a previous owner with regular steel brake line material, but it was sloppily routed. The lines were tight up against my lower radiator hose, which prevented me from changing the hose, therefore, I had to replace the transmission cooler lines first.
I did the job on a lift. It wasn't too bad to route the lines. The worst part was threading the nut of the upper line into the transmission, as there is not much clearance for a hand or ratchet. You want to start the threads by hand first, but it is a royal pain due to limited clearance. Once threads are started, I had to use a crowfoot-style line wrench, a U-joint and an extension bar, to tighten it, a little at a time. No leaks when I was finished, though.
