I haven't experienced this problem so far, but maybe it is just happening with the clutch/manuel transmissions. I did experience this in my younger years on my '69 Z-28. The rubber mounts wouldn't hold up. We cabled the torque side down. I had a cable made up with loops. I bolted one end to the frame, the other to the block with about an inch of play...never lost another motor mount... I did this with my big block '71 Camaro as well...same results. Any hardware can make you cable, and it is a cleaner look. I have even seen them chained down...