The GMC CCKW

Recently acquired a 352 that has replacement wiper motors fitted to convert to electric rather than air operated. I have tried to show a picture of the spindle hoping someone out there can advise what arms I need but any attempt to add the file via 'attachments' comes up with an error message telling me invalid file extension even though its saved as a simple word document and quite happily attaches to regular email. Help !

You can only save picture files. jpg is best. Must be a small file size.

Hopefully the picture now works, original was just too big a file. I am hoping someone out there may be able to identify a likely wiper arm that would fit the spindle. New motors fitted to replace original vacuum operation and the thread takes a 6mm nut although oddly the other one appears to be an older motor with a 1/4" shaft as a modern M6 nut doesn't quite work (1/4" = 6.3mm I think) ! Just need something that works for now in case it rains and will worry about authenticity later.

It looks very much like a Series Land Rover wiper, or early Defender style.