Build thread- 73 duster, forged 5.7 w/ PS and AC, 5 spd, big brakes and floater rear

Are you sure excessive heat near your slave and/or lines is not causing your loss of hydraulic action? You mentioned covering your lines near the exhaust. Wrapping the lines or cylinder will not keep them cool -only trap the heat. Best way to shield against exhaust heat is to use a heat shield between the exhaust and the slave or lines. This will reduce heat radiation and allow cooler air to flow around the slave or lines.
Heatshield Products has many to chose from. I'm going to use this type for my clutch setup. My slave sits right above the header collector and will definitely get cooked without a shield.