check yur pulleys, more importantly the harmonic balancer. I am unsure about dattos but in some older cars the rubber ring can perish causing the outer inertia ring to sit offset causing vibration. Just watch your pullies while engine is running, check it at different speeds as well. Also this is highly unlikely but double chect that you havent snapped a radiator fan blade off or water pump bearing collapsed. As for looking at the mounts, you might see that the rubber is cracked and perished but one way to check is to leaver the engine either a big bar or large screwdriver, or just jack the engine up and see if the mounts seperate, same applies with the gearbox.