OK...I added a line:
@QMAKE_CXXFLAGS += /MT@
The compiler warned me that it was overriding /MT with /MDd (which from the description on the MS page looks OK).
My executable only grew about 1K in size, though, which has me wondering if it did indeed pick up all the needed files during compilation. Running the app on my system isn't a good test (since I have all the libraries anyway), so I guess I'll have to find a system with an older version of Windows, huh?
Thanks for all the help...I think I'm at least on the right track here.