So I recently did a rear brake job as I needed to for inspection. I did not notice the rear brake line that was rotted where it goes up behind the heat shield as it crosses from the drivers side to the passeenger side. I failed state inspection. It was rotted where it was covered by what looks to be some kind of fabric conduit. So I spent about 7 hours today fabbing up a brake line and I'm back to square one. Apparently the lines are the wrong thread size. Boy they are very close but upon further inspection and measuring, the nut size measured .020" smaller in diameter than the original. I can only hope that I did not mess up the threads in the proportioning valve and brake hose. I have no idea why there are so many different sizes in this world. pisses me off to no end.

These lines are ISO flare (AKA bubble flare) but I have no idea what size. I was sold 3/16 but I know these are metric. I believe they are 4.75mm brake line. They seemed to thread in and fit good but when tightening they pulled right out. They would not tighten.Does anyone know exactly what size or specification they are? I have the OEM service manual but it does not state the size. Only states that it is ISO flare.
I'm sure glad I wasted a whole Saturday on my back playing contortionist for nothing.

I'm not sure if this is still accurate, but I know that all the lines used to be available through GM pre-bent and flared. At the least, it would save you the time and hassle of making new ones, assuming they still exist.

They are 4.75mm metric. If they thread in but wont tighten down, them you stripped the threads out.

I usually cut the new line, install the original nuts and double flare the cut back together after you size the length. Works every time like a charm.
I use a line bending tool to make the bends in it. Once you buy the basic tools your good to go on any car.

Heres a thread over on the T Type page that might be of use to you.

http://www.lesabret.com/phpBB/viewtopic.php?t=1564

Yeah, I had that exact problem...I got so sick and tired of trying to get it right, I spent $150 to have it done.

And also, if your crossover line behind the tank there is bad, check above the fuel filter. In fact, don't even touch it, you'll most likely break it..and if you do that, you'll have NO brakes. (I almost got cooked by a fuel tanker when I wasn't able to stop at a stopsign)

Thats the line I just changed on the SSE. The one over the tank. Removed the old one and fabricated the new one on the bench. Again it is simple with the right tools. Hardest part is getting on your back and installing it. Then bleeding with bleeders that are not cooperating due to old age.