Does anyone have any CAD/design files for these parts?
Essentially, no. Unless the ODK member who decided to reproduce the SB45 chassis in stainless steel did a set. And that would only be for the chassis structure.
The info ODK had, via our administrator Deejay, was that at the time the 45 series was discontinued by Rover/MTD, Golf & Bowling Machinery of Vic offered to purchase the drawings and tooling - but were refused. So it all went to scrap.