I removed the mount by putting the front of the car up on ramps, then putting my hydraulic jack under the oil pan (with a block of wood protecting the pan) and lifting the engine until the weight is off the mount. Most of the bolts are 5/8th inch. (You might find the engine lifts a bit more readily if the hood is open!)
Below, on the right, is the mount that Auto Zone's computer showed for a 68 Cutlass with a 455. It didn't fit. To the left is the mount I took out of the car. Advance Auto had it, #2261, for $6.95 each. These are made in Korea. If I find better quality ones, I will post that info here.

