Keep breaking motor mounts!

[66StangGuy]

i know its not accuriate but desktop dyno rated my setup at 425hp and 350 torque at 5500 rpm. i hardly run it that high but sometimes i do let first gear run out a bit. yes i do drive the car every day.. and i mean every day. theres always something to do and its my only car. as far as the trans mount i belive its ok but ill have to double check. do you think that maybe because of a bad trans mount im over stressing the motor mount? when i do break the mounts i break em good. compleatly tear in the midddle. 2 days ago i took of from a stop..no realy to hard. but i felt the pedal move away from my foot. i had felt this before and found it was the motor moving up and away from the drivers side. so i went home and opened the hood and powerbraked it and i could see the motor lift about 4 inches up off the frame. i let go of the pedal and wham the motor came back down. put another stock mount in and everything feels better now. just waiting for it to break again. i can still feel it flex now with the new one. is there something i can bolt in to make it not flex but not shake the car to pieces.