deadwoods

Hi. I've got a 1.4.6 MC running Forge 6.5.0.473. I want to upgrade to the latest Forge for MC 1.4.6. Do I; 1. Start with a vanilla MC 1.4.6 jar again and merge the latest forge jar into it, OR 2. Can I just merge the latest forge jar into the modded minecraft.jar (i.e. 4.6.0 + 6.5.0.473)? Thanks