I didn't go back and read every post but early on you state that you got a new clutch set from Brewer. What did you tell him you were going to be using your car for? Did they sell you a Hi performance disc? such as a Kevlar one? Those will grab,not slip on take off and will cause the symptoms you have. Other than that , mounts, motor and transmission. They might look OK but if they have never been changed out there 50 years old. Shocks , the same , they may look good but don't last forever.