I just picked up a '83 toy. Today as I was driving down the road, the brakes went soft. The pedal would be a little firm going down but would slowly go to the floor. I got home and checked the wheel cylinders, the calipers, the master cylinder, and I followed the lines front to back. I didn't see any leaks. After bleeding the lines just in case, nothing. I'm not sure where I'm loosing pressure. The truck has the stock rear drums and it has the vented rotor conversion up front. It still has the stock master cylinder. Any ideas?