Ian Osborne. Thank you for the link regarding the trunk light on ebay.
I think what you may be getting at is that the mercury switch within the light assembly would work with the 64 light assembly. Can anyone confirm?
I'm not sure if you were only looking for a genuine & correct '64 part. This one is close although the bracket looks different. It seems like it would function fine.
If you are just looking for the mercury switch to use, this might contain the right one.