Check the underside of the area you're going to mount the pulpit/windlass and see what the structure is like. You may or may not need to add any reinforcement. If there's at least a 1/2" piece of plywood there, glassed in, and depending on how much of the underside area it covers, you might be good to go with just your backer hardware. You could always add a little more, though, too. Best practice, when you cut a hole, is to oversize it then fill with thickened epoxy, then redrill the correct size. That way the wood is completely protected from water intrusion. You could also drill the proper size hole, then dig out a 1/4" of the core and then fill the void.
Are you sure you need to change your bow rails? Couldn't the pulpit slip out between the two forward stanchions. Then remount the bow light up top, or use side-mount lights. You'll also need to mount a new cleat, just off center of the anchor rode. I'm not sure if you have skene chocks and/or their current placement, but they may need to be moved.
Do you have a picture or your bow area? That may help me visualize what you're getting into.
What the anchor locker floor like in your boat? Do you need to build an actual floor and add drains?