THOMMO wrote:Hi Steve
The answer in that thread tells me,
that:-PO. 478.B, is to denote the fitting of a hydromatic.
The parts car I had in my possession had
- serial number:- EK225AUT - 2354A
The AUT being for the hydromatic!
What gives

Hi THOMMO.
Holden used several different methods of denoting the Hydramatic on the body ID plate.
I've seen EK225A, EK225H & EK225AUT on the MODEL line.
The other method is RPO 478. This can appear on the INSERT or TOP line. Sometimes this appears as just 478, but more commonly it has an A, B, C or D after it. This letter is different for the 4 different models that the Hydra could be optioned on.
Special sedans had RPO 478A, Special wagons, had RPO 478B, Standard wagons RPO 478C & Standard sedans RPO 478D.
I'm not sure with this differed from factory to factory or it changed over time, but the only way we will learn is by posting & recording as many ID plates as possible.
Dr Terry.