A tool to tell you what source files are needed in a C++ project?

I am porting a large, messy, 10 year old cold base in C++ from Metrowerks on OS X to XCode. There are so many files and all the other people that touched this over the years are gone. Nobody know what files are actually needed and which are just cruft.

Is there any tool that I could run and have it produce a list of what files are ACTUALLY needed?

You could run doxygen on your project and have it generate inheritance diagrams for your classes. It can also generate caller graphs to help you find dead code.