Hello there
Please find below the advice from my friend in Oz , John M who knows a lot about these early 4/4s
The specified grade is SAE 140 EP. May be a little stiffish starting from cold but soon frees up. Lighter oils eg 80-90 EP generally OK but inclined to be a bit noisier.
The filler plug is to the rear right side of the gearbox near the speedo take- off. Fill through here until oil starts flowing out.
Hope this helps
Best regards
John