Hello rocknmg01,
The Cisco 2651XM was discontinued a few years ago:
- End-of-Sale and End-of-Life Announcement for the Cisco 2600XM Series and the Cisco 2691 Multiservice
The Download Software site on Cisco.com does not even offer the option to get the old IOS releases for that platform anymore.
It is highly possible that support for IPv6 EIGRP is not incorporated on the releases available at the time for the platform (I'm not completely sure though).
You might be using GNS3 for educational purposes. Recent IOS images for the Cisco 7206 VXR are still available in Cisco.com
I hope this helps.
Best Regards.