Yes. You must get rid of the forward brake line t-block. This is a brass fitting that is bolted to the drivers-side frame rail right next to the lower radiator hose. For the life of me...I don't know why this is here, as all it does is make the rear brake lines longer. The steering box bolts to this area, so the t-block must go.
There are (4) lines that connect to it...RR and LR. First thing you must do, is label the ports at the master cylinder and also the (2) lines that run aft to the rear axle. You must keep these brake lines organized, because they will need to be reconnected to the correct ports at the master cylinder. After you get everything labeled...remove the t-block and the (2) lines that connect the block to the master cylinder. This can all be discarded.
When done...you will have (2) brake lines open-ended where the t-block used to be...and they run the entire length of the truck to the rear axle. Take some time to straighten them as best as you can...they are very hard to bend. Next remove the plastic clips from the frame rail...all the way back to the tranny crossmember. This is necessary because the upper 3-link mount gets welded to the inboard side of the frame rail, and the brake lines must be bent (by hand) to clear it.
Now you must bend both of those brake lines up at the firewall and route them to the master cylinder. They will be slightly longer than what you need so I find it works best if you put a service loop in them right at the master cylinder, (I run them past the ports then put a tight 180 bend in them). The original fittings (formerly at the t-block) thread right into the master cylinder. Make sure you get them connected to the correct ports. Check to make sure the brake lines do not rub on the steering shaft, or any other items.
Bleeding is pretty standard except you must have the ignition on to bleed them, as the H3 uses an electric brake booster. The factory brake lines are plastic coated and they are a total beyotch to work with. I use a small piece of 1.5" DOM to form the bends, as my tubing bender does not fit them. Forget trying to cut and re-flare them...it works much better to save the factory ends and fittings, and reshape the lines to suit. If you do end-up mangling the brake lines beyond repair...you will be forced to replace the entire line with an aftermarket piece. These plastic-coated GM lines are impossible to modify.
Here's the t-block and lines to the m.c. that must be removed...