you should be able to use them to set up an ipsec tunnel between them. you might not be running a version of cisco IOS (the operating system of the routers) that supports that though. this might cost you a little money to upgrade. you might also need to upgrade the router's flash and/or ram to support that new version of IOS that support ipsec and vpn tunnels.
do you have access to the routers? can you do a show version on each ? that should tell you most of what you need to know