A correctly placed frontal or side head/brain shot with a high quality solid ( Barnes, Woodleigh, etc) out of your 375 will cleanly kill the elephant. Pick the 300 or 350 gr bullet that gives you the best precision. If you still want the 458 but have not bought one, the go with the 458 Lott. Look at a pre-owned CZ 550 Safari. CZ quit making these in 2020. I borrowed my PH's in the Outback and killed two fine buff. Well made before 2020. As for elephant, I have killed two, both with Heym Express bolt rifle in 500NE. Look at Ammoseek.com for ammo.