It's that master 4 wheel disc specific? I'm assuming most without ABS had rear drums, but I could be wrong (mine was drum even with 5.0)Booster or master? I assure you it’s no myth. However the better way to do is is using the standard 89-92 Thunderbird booster and 4 port master cylinder and simply blocking off the fourth port with a bleeder. If you can get the lines off the stock ABS master without destroying them it’s literally plug and play with some minor rebending. That’s how I’ve done it