Depends on what you plan to do with the t1.
You could just only use the WAN addresses and run nat overload on it and ignore the lan ip's
You could put static nats in for the new LAN ips and map them to your current private network. Unless you are using the very latest version of NAT you will need to put a static route for this lan subnet to your fa 00 to get nat to work. You can also use one of these as a pool if you work at it.
You can put a secondary address on your private network interface and just overlap the networks if your really want to use these lan addresses without nat.