Hi Stew,
History of the Mowmobile here below.
https://outdoorking-forum.com.au/forum/ubbthreads.php/topics/78250/owen-cox-mowmobile-c1963.htmlThey are worth a few hundred to mower collectors ,the 4 and 5 hp motors can be found second hand on
other mowers and you may still be able to get new parts like piston rings online and air filter, carby rebuild kit,
the 6 Hp motor may be more difficult to get parts for unless some 5 Hp parts are interchangeable.
If you needed parts for the mower excluding the engine (like Wheels etc) you would need to make them or buy another second hand Mowmobile to get parts from it.
I've never seen what a restored one would sell for ,just occasionally see them advertised for $300. or less
but at that price they are rough looking mowers.
Cheers
Max.