Can you elaborate more on the detail requirement ? What is Business Cable, what is the bandwidth ? Why replace the 2600 ?
You have to design how it fall-over to the backup and what traffic will be fall-over during the primary link down.
Are both T1 active or load-sharing ?
If there are only two sites, simple to use floating static. If there are many sites or sites behind two nodes, you may need to deploy dynamic routing protocol and fine tune the route for preferred path.
More info. can be better.
Hope this helps.