If you can find the buyer with sentimental appeal and deep enough pockets, I imagine you could get as much as $800. I'd probably pay that for an early 70's Fuji Special Road Racer in my size, if it were still sealed and had been stored well(no rust).
If you list it on Ebay/CL at $400, it might sit for a while. An Ebay auction might go for less.
Overall, I think this is hard to judge, as it does not come up often. Most people would consider it junk too. There were some old bikes listed on Chicago CL not too long ago, which were NOS out of a local shop that closed. I think they were selling around $250-300.