Luke,
The Aust Ford CMPs assembled and stamped with their chassis number/engine number locally, have the stamping as previously indicated, so you won't find it stamped on the vertical of the chassis rail. The FGTs certainly fall into this group.
The number is often quite lightly stamped, so some judicious use of wet & dry might show it up. It will be something like the format '3GXXXXF' or similar.
Once you locate the chassis number, I'm pretty sure Keith or I can narrow down an ARN pretty quickly.
Mike
