Wildcatter264
WOW some extremes. As you are looking for suggestion, everyone has an idea, however it is in your ball park to make a decision on what you take.
1st rifle
Your 450 for elephant will do the job provided you do your job and have good bullet placement. Scope or open sight, both should be a fun hunt. If you are using a scope, may i suggest you have it sighted for 25 to 50 Yards as you will usually shooting at under 20 yards.
2nd rifle
I would take the 338 WM and Barnes 225 factory loads. sight it dead on for 200 yards and your good to 300 + yards, or what you set as your limits, i limit my shooting to 350 yards and under off shooting sticks.
Using the above, i have taken two shots and 2 giraffes. one giraffe dropped in it tracks, the other giraffe went about 20 yards and fell over. Study a giraffe make up for good shot placement.
