When we built my youngest son's truck, I wanted to use a Line-Lock in the brake lines for a parking brake and to hold the truck in the water box for a burnout to heat the slicks, but couldn't use a commercially-available electrically-operated unit because they will overheat and fail as a parking brake. I chose a lever-operated hydraulic ball valve and mounted it between the seats. You can use all four wheel brakes or only the rear brakes or only the front brakes, depending on how you plumb it. I installed it to operate only the front brakes so that it worked well in the water box and as a parking brake. The valve remains open and all brakes operate normally until you press the foot brake and turn the handle 90 degrees. Then you have locked hydraulic pressure into the line and you have a parking brake until you turn the handle the other way 90 degrees and release the fluid in the line to the front brakes.
These installation instructions from Allstar will show you how to plumb the valve.......disregard the electrical part of the instructions......
Use a hydraulic valve rated for a minimum of 2,500 psi.