I know when I done mine I had to jack one side up more than the other which was a bit of a pain as the fan was hitting the shroud... It's painful jacking it up so high, i really didn't like it! I know mines a m30 but same horse different jockey I would imagine. I hope all is ok, someone with an m50 will confirm if it's the same deal, as I'm sure it's been done a million times before. Have you put the engine down with the new mounts? Maybe the mounts had collapsed and left the engine sagging?