I can almost guaranty you that there is some surface rust down in there regardless of how the car was restored or maintained. So I'd avoid using any water. Instead, get at it with compressed air - a thin piece of hose on the end of a spray nozzle will give you better access and won't damage the painted surfaces. Blow out any crud and then wipe any area you can easily access with a DAMP rag. Remember, if you can't see it nobody else can either!

If you're trying to clean up the quarters, stuff towels down into the trunk extensions. Then use something like Spray Nine on the quarters and a soft scrub brush then a wipe with a damp rag to clean up. The towels in the extensions will keep the dirt and water from getting down in there.

So how did they get so dirty in the first place ???