The configurations for the specific kernels shipped in Fedora Core 5 are in the configs/ directory. For example, the i686 SMP configuration file is named configs/kernel-<version>-i686-smp.config. Issue the following command to place the desired configuration file in the proper place for building:
cp configs/<desired-config-file> .config
You can also find the .config file that matches your current kernel configuration in the /lib/modules/<version>/build/.config file.