Airport Extreme as Ethernet Bridge

I have a Time Capsule connected to my modem as a router and via an ethernet cable I have an Airport Extreme connected in the garage at the opposite end of the house. I want to the Extreme to Bridge the network and either extend the wireless network or create another. Should be simple. If I set the Extreme to Bridge mode and extend the wireless network it forces the bridge to wireless (any other option is grayed out). If I try to create a new wireless network the Airport utility insists that I plug the ethernet cable into the WAN port. If I do that then DHCP conflicts happen. There is something simple I'm missing.