Just to be clear, the functional equivalent mount kit for the combined one that now ships with the AP-305 is AP-220-MNT-C1, not -C2.
The C1 kit attaches to the same two flat mounts as the combined one, but this kit has the original two separate pieces. The C2 kit is indeed for other rail types.
The metal CM1 kit will work as well, but is indeed a bit more difficult to install.