switching to conventional brakes
The "low line" description was someone else's in one of the above posts, that I took to mean a non supercharged, regular T-bird, which has a regular brake booster, and diagonal braking system.
The block you refer to low down on the frame, is for the rear brakes. If you trace the 1 line from the back of your car,(I assume you have a Super Coupe you are doing this one, with 1 brake line tothe rear of the car, instead of the "low line" car with 2 brake lines to the rear. Anyway, trace the 1 brake line forward, and you will fine it goes to this block. Plumb the rear-most line (the line on the Crown Vic master cylinder) that is the closest to the firewall into this block. The line on the front of the Crown Vic master cylinder goes to the splitting block from the Crown Vic. If you look at my photos closely, hopefully you can see that I did NOT use the wiring from the Crown Vic block. The plug is still on there, but the wires are sticking out about 3 inches, and go nowhere. I just haven't bothered to take it off. The 2 lines from the Crown Vic splitting block go to the 2 separate front wheels. One line goes behind the booster, and across the firewall to the right front wheel, the other one straight down past the "other" block to the left front wheel. I'll check in again periodically if you have any questions. Good luck, remember, don't let your kids or wife, or your pastor in your garage when you start working on it.