Just had my front Diff seals replaced and the transfer case shaft seal (sorry, no part numbers listed on my invoice so unfortunately I cant provide this) and I too didnt have any info to offer them. So when they extracted the front diff seals they used the old ones to obtain replacements.
For the Atlas seal they contacted Atlas - said they were the greatest group to work with. Instead of having to wait for a new seal to be delivered, Atlas revealed the options (local parts store had it). Atlas also took time to talk with the Mechanic to explain the process and provided torque specs so everything would be done correctly.