Little too broad of a question to be able to answer.
It depends on what the typical market participant in your neighborhood would expect from a home of built in that era of that size in your neighborhood. I would check out realtor.com for similar aged homes in your neighborhood. Your "neighborhood" is a tricky thing to define without doxxing yourself. A safe bet (though not 100% as there could be other mitigating factors) would be too look at school district boundaries. Is your district superior or inferior to neighboring district? If equal then it is less of an issue but if there is a stark difference stay within your boundaries. Also, 1 mile is sort away is a general rule of thumb but it is not hard and fast and again there could be other mitigating factors.
Anyway, look for homes similar age homes of the same or similar design style that are within a 25% differential of your above grade living area. Look to see if there is a price difference between homes with finished basements versus homes with unfinished basements. What is the height of your basement ceiling? Often homes of that era have basement ceilings under 7 feet. If it is under 7 feet then it will most likely not be counted as livable space. Again it depends on what the typical market participant would expect.
Does your basement have egress windows? Is plumbing roughed in for an additional bathroom?
The more information you provide me the better I can point you in the right direction, of course it will still be speculation without knowing your specific neighborhood, current market conditions and current supply & demand dynamic.