Wow Nissanman, is there anything you don't have a picture of?
AS Nissanman said, most old yank cars had red indicators. I've seen lots of old Chevs and Cadillacs with the rear/brake light and the indicator as one single unit, so when the car is braking and indicating, only one light is operating as a brake light, and the other is the indicator. I don't know if these would be legal on a Datsun, but you could use your idea with the reversing lights, or even mount an aftermarket indicator under the bumper. You can get some pretty retro ones from eBay, they're mainly marketed for hotrods or Harleys, but no reason why they can't go on a Datsun.
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green200b - aka Alistair
The fleet:
Australia:
'80 200B GX - the
green200b - hibernating
'81 RX-7 - 12A extend port - daily
'74 RX-2 - 13B bridgeport - cruiser
Europe:
'93 200SX - CA18DET - tourer
Green200B has forgotten more about 200Bs than we will ever know.