The company I know of, and that seems very serious about doing this type work, is Crewe Engines (creweengines.co.uk). I got some documentation from them and it looked good. I have no experience with them, though. Maybe someone else here does? You can get a quote from them. There are a few unknowns though, like what the condition of your engine is now - whether the head is good or not, whether the engine needs to be resleeved, condition of the crankshaft, camshaft, etc. etc. Generally quotes for a full rebuild that I have seen range from Euro 5,000 all the way to more than double that, for essentially the same work. So it pays to shop. That price excludes the removal and refitting of the engine which can take another two days of labour.
Cees Klumper in Amsterdam
'69 white 280 SL automatic