Hi. I did this recently on my 1952 11BL. I removed the rear engine bolts from inside the car and then using a hydraulic jack and pieces of wood under the sump, I lifted the engine very slightly. That gave enough clearance under the manifold to get the motor out. I have now fitted a modern alternative (from wosp) which is much smaller and hopefully will be more reliable.
Cheers
Terry
Thierry Gest