Upon reflection would I use the same 338 WM rifle??

Probably not!!

Compensating for the wind gusting to 20+ mph was annoying and a challenge for taking the sharp eyed Black gnu after multiple stalks to get to within 225 yds.

I hate to say it but if I were to do the same things again,4 stalks, and 3 ambushes I would use my 338-378 WBY shooting 250gr A Frames at 3000 fps. Less wind effect and flatter trajectory.Under less unusual conditions of severe drought not concentrating the animals so much with the resultant zillions of animal tracks/sign and with more timely selective tracking/stalking of any plains game taken I feel my 35 Whelen bolt would do just fine and be just as exciting.