From my somewhat limited African experience, having shot or seen shot Gemsbok, Kudu, Zebra and Eland.
The 30 06 will do the job, but it wouldn't be my first choice; would far prefer a 338 Win Mag for awkward situations and exits, entry wounds don't bleed enough.
Gemsbok will go a long way if not hit properly, need reliable combination of expansion and deep penetration, I'd use 180 grain A Frames or Northfork.