The auto or manual can easily be removed from the V12 without pulling the engine. Here are the steps.. This is basically a 2 hour job with a lift and basic hand tools.
1. Inside the car, remove the shift knob and tapered base chrome finisher on the manual cars. If automatic, go to step 2.
2. There is a pipe that is threaded on both ends that holds the two sides of the car in place. It goes between the engine and transmission. The bolts are accessed from inside the car by lifting the carpets on the tunnel. Go under the car and attach a pair of vice grips to keep it from turning. Note the location and it will make it easier to find the bolt heads inside the car. Remove both bolts. The pipe will fall on the ground. Note that you will probably need some help putting this back in.
3. Under the bonnet, remove the bolts and nuts that hold the upper front picture frame in place. No need to drain the cooling system or remove the header tank. When done, pry the cross piece up so it is loose from the picture frame.
4. Now under the car, remove the exhaust from the olive flanges at the downpipes back. No need to take the system apart, just set aside as a unit. Drain the oil on either transmission. Remove dipstick on automatic from transmission. You can leave it hanging in place. On the automatic, there is an access point on the left side of the car to access the torque converter bolts. Remove all 4 at this point.
5. Now unbolt the front motor mounts at the base with the 5/16x24 bolts and nuts. Remove bolts and note the spacer/insulator plate for putting back when assembling
6. Place a jack under the rear of the engine or transmission and lift the rear of the transmission until it hits the tunnel. Remove the rear support plate and brackets. Note the spacers and their position for reassembly. Lower the jack to access the driveshaft bolts and nuts. Remove and press the driveshaft rearward enough to clear the transmission flange. Remove the jack and the rear of the transmission will drop some more. It will not drop out of the car.
7. If automatic, disconnect the shift lever and cable bracket from the transmisison.
8. Place a jack with soft board (2x4) under the oil cooler area and gently jack up the front of the engine. As it goes up, the rear will drop. When the rear transmission flange clears the body, stop. Install Transmission jack and remove bell housing bolts. If automatic, remove vacuum line and kickdown wiring.
9. Lower transmission out. On the manual, it might be necessary to tilt the transmission slightly to clear the torsion bars.
10. Drop the transmission. Install is reverse of the removal.
11. Note that there are no modifications to the car and no cutting, grinding or trimming.