Poor old uncle Bill. My sympathies to you!

Assuming the three rifles are identical except for caliber and weight I would agree with Mickey - choose the .375 Flanged Magnum. It's more versatile in North America than the .450/.400, and it is adequate for Africa.

This all assumes your are a dedicated reloader. If not, you may consider the .375 Belted for availability of ammo. But in that event be prepared to take a lot of "chin music" from others on this forum who think the gazillions of DR's chambered in that fine round are virtually worthless because of rimless extraction and high pressure.

Curl