You can't tell Visual Studio to use an earlier version of the runtime library. Even if you can get it to compile with the old library, the application itself is not going to run correctly because the compiler is going to insert calls to functions it expects to be in the library, which might not be the case.
also I want to avoid static linking msvcr
Why? That seems like a perfectly valid solution to this problem. Sure, you pay about 100kb in code size for it, but that's worth it over being forced to use Visual Studio 6's buggy and nonconforming compiler.
You could also just include the MSVC++ redistributable which would contain the correct DLLs and wouldn't require static linking of the standard library.