Oh, sorry. I can understand at $2.10 each you are trying to save these, but I can tell you from experience, it won't be easy.
If you have an early car, pre- TS60000, the studs will be a combination of wood-screw and machine screw. Later cars had studs with sheet-metal screws into the dash top and machine screws elsewhere.
After 50 years the studs attached with nuts are probably frozen with rust and it's unlikely they will come out with out being destroyed. If you have any that are screwed into wood try this old trick. Take a soldering iron, at least 100 watts, let it heat up and touch it to the end of the stud. The heat will be conducted through to the threaded end and sometimes will be enough to loosen the wood screw. This has worked for me when trying to take out very old door hinges in old houses.
Because of their shape, a conventional open end or box wrench may not be best. I would suggest a tool like a nut driver. You can get a set with several sized 'sockets' at Sears - not too expensive. You may have to try several size sockets until you fin one that fits and they may not all be the same. It may be that the best size is going to be metric.
good luck