All of the Victa full-crank 2-stroke rotary mower engines had 1/2"-16 BSF threads on both ends.

The long nut is fairly easy to find, as it was used in combination with the lanyard type starter pulley on the earliest models. It also saw use on some later models, if retrofitting a pulley in place of a wire rope or impulse starter.

So just about any 2-stroke Victa wreck with a lanyard pulley will have one.

The stepped bolt will be a bit more difficult. I'd be looking at getting a 1" long 1/2" BSF hex set screw [which are fully threaded], making a slip-on locating collar for it, and cutting it to length.

There are a few specialist fastener suppliers who have these. A Google for 'BSF set screw' finds a few.
Blackwoods are probably the easiest to find, and they list them: https://www.blackwoods.com.au/part/01620706/screw-set-hex-brt-bsf-12x1

Cheers,
Gadge

"ODK Mods can explain it to you, but they can't understand it for you..."

"Crazy can be medicated, ignorance can be educated - but there is no cure for stupid..."