Yes, that blade was designed for Sup720 and you have a Sup720. You should be fine.
http://www.cisco.com/en/US/products/hw/switches/ps708/prod_bulletin0900aecd800f6e27.html
"As the premier modular multilayer Cisco switch for integrated data center switching, the Cisco Catalyst 6500 Series now offers a new, high-performance 48-port 10/100/1000 Ethernet over copper module designed specifically for use with the Cisco Catalyst 6500 Series Supervisor Engine 720 in data center and distribution layer deployments."
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