Can i just overlay it on a base map and make the fit as close as possible? (the scanned map I have has decimal degrees but its really old and doesnt seem to align to WGS 89 which is the coordinate system I want.
The difference in the projections and you are going to reference it to requires control points.
You can adjust to fit as best you can, but you will need to provide that real-world referencing in order to get a useful product.
It looks like there are graticule lines identifying latitude-longitude so you could use those. If they aren't labeled with latitude-longitude lines, are there any coordinates on them at all? Is there any projection, datum, or ellipsoid information anywhere?
Who's the publisher and when was it published? That can also help narrow down what coordinate system was used.
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