Here is the skinny on your problem.
The brake line is a standard size and not a metric. But the fittings are metric.
In my travels, I have done the job you are about to do. There is some do's and don'ts to that job.
The don'ts is - don't try to splice in a new line. The brake line runs across the top of the frame rail from the anti lock module to the rear end housing. It runs behind the rubber skirt in front of the wheel and behind the rear wheel and then it makes a 90* turn and goes around the front of the spare tire and then connects to the T in the line that is on the frame side of the rubber line that goes to the rear end.
You can use a NAPA 641 - 5474 line kit, 1/4" x 25'
It costs about $40 - depending on where you buy it.
It is a poly coated brake line that will last a little longer then the original.
You will be required to buy or have a double flare tool, because a single flare will not work with this line and the fittings.
The fittings are a metric thread with a SAE nut head.
The fittings are sealed from the factory with a thread locker and will require you to heat it up with a torch before you will be able to remove it from the ABS unit..
To get the line off the ABS unit, you will either need a saw or some type of cutting tool - because the only way to get the old nut out of the unit without damaging it is to use a 6 point socket. I think it is either 1/2 or 9/16ths.
You will need to cut a wrench in half - about 3 or 4 inches long to be able to tighten the nut once the new line is made. There is not a lot of room around the ABS and it is sometimes easier to tighten from the top then from the bottom.
What I did was unroll about 12 feet of line and snake it under the wiring harness and use a tubing bender to make the bends in the line. Once I got it from front to back, I zip tied it to the harness. The clips are pretty much useless on top of the frame rails - unless you remove the body to replace the line.
You need to make a 180* bend for the ABS and it has to be pretty tight, about a 1 inch radius. Remember radius is half the diameter.
I was told by others that you can buy line in one foot increments and then cut it in half and use the nuts and throw the line away. But where I live, I could not find a line with a SAE nut and a metric thread.
When you get to the rear end, you will need to make another 90* bend to connect to the block. It is usually easier to remove the spare tire then to try to do it any other way.
If the line blew, you are going to have a fun time bleeding the lines. Try to use a 1 man bleeder. I was told that you can remove the electric plug from the ABS and then reconnect after you get the line bled.
If you cannot get the brakes bled, you will need to take it to a garage where they have a tech II tool that will pulse the ABS for you.
It is my experience that once you climb under the vehicle, you will find that there is not enough room under the vehicle to remove only part of the line and try to splice the line. You will also find that the line is usually rusted beyond repair and no place in the line from front to back will be strong enough to use a compression fitting.
So pretty much, you are screwed until you make a all new line.
Most mechanic's will tell you that if the one line is bad the others can't be too far behind. You might want to replace the two lines that goes to the two front wheels while you have the truck up on jack stands and the fluid out of the system.
Come back please and tell us how you made out.