Very nice conversion. Two weeks for a professional or person close to being a professional, I'd say. Well done. But what is the motivation? Is it for the fun of it, or just a spare mint W116 chassis?
When my 6,9 engine is dead, I think it'll be replaced by a modern 3 litre turbo diesel - same torque, nearly the same power, and 2-3 times improved fuel economy. Or how about an electric conversion - plenty of space under the bonnet or where the fueld tank goes - ideal for those of us who do 50 mile trips tops.