So, doing a little searching, I dug up this:
Definitely the 5-0 light.
Every slicktop I've been finding seems to have a revolving dash lights with round deck lights. But when you get in to the 90's, they seem to have long rectangular deck lights.
This guy has a red 5-0 light for sale for $50 (probably could offer less):
http://elightbars.org/f16/prices-adj...ll-stuff-5640/
I think it would be a good thing for a MSP restorer to snag up and hang on to.