Some supplemental info to Spidertrax' excellent installation instructions for their Brake Line Kits. I've only dealt with the kit fitting a 1988 Samurai (dual diagonal braking system) so that's what you'll find below.

Tools

Preparation

Be prepared for a minor mess. You'll be opening brakes lines and fluid tends to run everywhere. Make sure to promptly wipe up fluid spills on painted surfaces of your truck (unless, for some reason, you want the paint removed). Brake line plugs can make things a bit easier and reduce the potential for a mess, but they're certainly not required.

Note: Since disc brakes tend to heat up more quickly than drums, and since there were now going to be discs on all four wheels, I elected to use synthetic brake fluid for this project. Virtually all of the old fluid was going to end up drained, making this the perfect opportunity.

Synthetic fluid costs roughly twice as much as your run-of-the-mill brake fluid (I found quart bottles of synthetic for about $4.50) but has the advantage of not absorbing water like standard fluid, as well as handling heat better. Cost-wise, use of one over the other is likely to be about even. You should change standard fluid more often than synthetic, so you pay two times (at least) for the standard while you're only paying once for the synthetic.

	Disconnect and remove the original rigid lines at the rear axle. There's a series of clips to open and the lines lift right out when disconnected. The easiest time to do this is while installing Spidertrax Rear Disc Brake Kit.
	I put temporary plugs in the rear lines while I completed installation of the rear discs. Don't forget to remove any plugs when assembling. If you have a later model Samurai, there will only be a single brake line at the rear axle.

Assembly

	After removing the protective cover over the lines, here's the way the manifold will look in the stock configuration. You're going to swap the connection at upper right with the one at lower left to convert from dual-diagonal braking to split front-to-rear braking.
	Partway through the swapping process. The line that was at lower left has been (gently!) re-formed and reconnected at the upper right manifold position. The line that was originally in the upper right manifold position is the one looking like it's now connected at the lower right. Actually, it's just hanging free. I chose to cut and re-flare the line that will end up at the lower left position, as it was cleaner than trying to straighten the sharp bend and re-bend the line to fit. Either way, removing this line completely to make the changes is easier and less likely to cause problems than trying to re-bend it in place.
	A front view of the proportioning valve and brake lines. Make sure all fittings are properly tightened. The large red portion on the proportioning valves outlet fitting seen here shows that I hadn't yet tightened the fitting properly.
	Two more views of the proportioning valve's lines and fittings. In both, the line connected to the union fitting in the lower left foreground is the line that was originally attached to the master cylinder (seen at lower center in the pictures). The fitting in the center foreground on the proportioning valve body is the valve inlet. Check the markings on the valve when installing it to make sure you have the inlet and outlet sides correctly oriented.
	The new rear axle lines in place and reconnected. (Did you remember to remove any plugs?) The shiny black spots on the axle are where I removed some (now unnecessary) mountings that were used for the stock emergency brake cable and then repainted.
	A slightly wider shot of the new brake lines as installed. The stock lines were wrapped with some sort of protective rubber material wherever they passed through a clip on the axle. Spidertrax lines do not have this wrapping. I inserted small pieces of fiber reinforced rubber sheet cut from some scrap material to ensure that the clips did not damage the new lines.
	The overall brake line assembly at the rear axle. Again, shiny black sections are where I cut off mounting points made unnecessary by installation of the Spidertrax Rear Disc Brake Kit and the Spidertrax E-Brake Kit.

Finishing Up

Clean up all the brake fluid spills and dribbles. Fill the brake fluid reservoir. Re-check all fittings to ensure that they're tight and leak-free. I was at the end of a day here, so I just made sure that all fittings were closed and then let things sit for a couple of days and 'gravity bleed'. Much of the air in the lines will percolate to the reservoir just by letting things sit for awhile.

Top off the reservoir. To get started, open the bleed ports on both rear calipers and allow them to gravity fill and bleed until you begin to get fluid out the bleed port. Keep a sharp eye on the reservoir level. Close each port when you begin to get fluid.

I used a Mighty-Mac hand vacuum pump with its brake bleeding attachments to start bleeding the system. With this little pump you can do most of the brake bleeding alone. Just remember to re-check the reservoir at frequent intervals to make sure you don't pump it dry.

Starting at the furthest point (passenger side rear wheel) hook up your vacuum pump and bleed one wheel at a time, rechecking the reservoir level frequently. Work to progressively shorter lines as you bleed the system. In order: right rear wheel, left rear wheel, right front wheel and finally, the left front wheel.

Once you think you've got the majority of the air removed, get someone to help you finish up. Complete bleeding the traditional way, again starting from the right rear. Check for leaks during this process, as your assistant pressing the brake pedal will pressurize your new bake system, where the vacuum pump did not.

Finally, adjust the proportioning valve as per Spidertrax instructions and then test, test, test the new brakes. The last thing you want to do is find some overlooked problem when you're attempting a panic stop from 70 mph on the freeway. It may be the last thing you ever do. If you can't get things right, carefully drive to a brake specialist and have them make it right.

Problems