direct connection between 2 offices

I am trying to setup direct connection between company A and company B. the two companies are located in different states. A will function as main office and B will function as branch office. All the traffic from company B will be routed through company A. the 2 companies right now connect separately to the internet. Company B using fractional T1 and company A using ATM. Both use Cisco 1720. The idea is to integrate both LANs. What are the options available for this scenario to establish the connection and what equipment needed?