I have a solid driver side mount and a stock passenger mount on my mild 360 (300ish hp). No problems at all on street and occasional 1/4 mile runs. No bad vibration with my 268/285 cam. I have read (probably on here) that in high horsepower engines and/or cars that hook really well, it is possible to crack the mount ears off the block with a solid drivers mount. So if you're in that camp, maybe the engine plate is the way to go. My hp is too low and the car doesn't hook enough on Radial T/A's for this to be a concern to me.