That clutch body is totally shickered and I would now be rather sceptical about the integrity of the engine mounting rails to see if they have stress fractures within them or not, but with the look of the output shaft and the clutch condition it's highly likely that you're in for the long haul here.
Clean all the grease and grime away and please take some close up shots of the areas around the 4 engine mounting holes.
Going back to your engine, it all depends on what you are chasing as an end result. Is it an all original looking mower of just a fully functional mower to use as a daily driver. Once I know the answer to that question only then will I be able to answer the questions in the right direction for you.
Cheers,
BB.
