Hello BNeville
First of all, welcome to the group! And it is great that you became a full member straight away.
As to your question, the numbers that you have posted are not of the engine, but the cylinder head. There is an excellent chart on what these numbers mean in the technical manual. That said, the numbers do indicate that you have a 280 engine in there so your original engine was replaced at some point.
Have a look at that section of the technical manual, as it explains all about where to find the actual engine number, how to interpret it etc.