Looks the commands are hidden however I was able to still configure them on a 3048.
3048-BF3# show tacacs+ status
distribution : disabled
session ongoing: no
session db: does not exist
merge protocol status:
last operation: none
last operation status: none
3048-BF3# conf t
Enter configuration commands, one per line. End with CNTL/Z.
3048-BF3(config)# tacacs+ distribute
3048-BF3(config)# end
3048-BF3# show tacacs+ status
distribution : enabled
session ongoing: no
session db: does not exist
merge protocol status: not yet initiated after enable
last operation: enable
last operation status: success
But after completing these steps it appears that the config from the primary for tacacs does not replicate to the secondary peer. Might be a platform version issue as this working in the 7k platform.