I installed the engine on the airplane today.
In the end this was not a difficult job, at least, if you have an engine hoist. Just set the hoist at the right height, slide the engine in place and install the bolts.
It's a very satisfactory exercise though.
With no wings or tail on the plane it would tip over (only just, you can hold it in place with one finger) with the weight of the engine hanging from the front of the plane, for now I'm leaving the hoist in place but I will attach a weight to the tail later so I can remove the hoist.