Mixed opinions on this. Most of the big guys are going to run solid with the motor being held solid in 3 spots. The mid plate gets mounted to the frame on either side and then the motor mounts at the front of the block (location the industrial applications mount there mounts (no pun intended!!!) The block is much stonger in this area than where the standard dodge mounts go.
I have heard by the gasser guys in the past that frame flex isn't always a bad thing and somtimes an advantage to plant the tires. On a 4x4 if the fronts are barely scratching the dirt its not doing much for you but if the frame is flexing trying to lift the left tire its also planting the right tire.