Hi Weary!

Yes, it will require some thought.
I hope the casting can be repaired - at least for static display.

Some parts for the engine should still be available.
Here is a picture of a similar engine on a highly-collectable Australian Grasshopper:-

[Linked Image]

It would be great to give us updates from time to time, as this site
has a considerable number of vintage mower enthusiasts.

Cheers.
-----------------------
JACK.