Several things will determine the value of the car.
1. Does it run and how well ? This is rather obvious but it still important. A running, all original car is worth more than a dead one. So some money spent on a tune-up, battery, new hoses, etc. will pay for itself.
2. Inspect the exterior and interior thoroughly. Rust, oxidation, and rot will devalue the car big time. If mice/rats/bugs have taken up residence in the car at some point in the past, prepare to lower the price or spend some money to clean it up / repair it.
3. Look at the tires and all the rubber hoses, if they are dry rotted or cracking then they have become a safety hazard - its buyer beware or they need to be replaced.
4. Hagerty Classic Car insurance has a good tool to get you in the ball park. Obviously the car is worth whatever someone is willing to pay for it. However, here is the link to give you a starting point.
https://www.hagerty.com/valuationtools
As for marketing the car, that depends on you and your neighbor. How much do you want to spend? How much time are you willing to invest in trying to sell it? Selling vehicles on Craigslist, eBay are popular. Some people feel websites national websites like Autotrader.com are a good way to go. Advertising in magazines like Hemmings Motor News is always a possibility. Each option as varying costs and reach. Let's not forget advertising in your local newspaper or Auto Swapper.
If you do anything online, the more pictures - the better to attract a potential buyer. Some sites limit the number of pcitures or the file size (of the picture in terms of storage size), but use as much as they will allow you to.
Does that help answer your question?