I do not have the experience in Lion hunting but this sounds like a question for your P.H.

MD73, if I were going to use a 458 Win Mag for lion hunting, which wouldn't be my first choice, I would hand load a 480 gr Woodliegh soft point to about 2100 fps, and make sure it hit the right place the first time.
What I mean by this wouldn't be my first choice for lion hunting in general is, lion hunting is done in several ways, and for all except over bait, the 458WM isn't my idea of a lion cartridge. In any event, I wouldn't use a .458 bullet of less weight than 480 grs. Even 500 gr bullets have been known to not pennitrate the full shoulder if a big lion. You need that SD of a heavy bullet.
If tracking, or simply drive-spotting, many of the shots will be long, and most at a running animal. For this a good 375 H&H, or 416 Rem Mag is a much better choice, and actually either of those pennetrate better then a 458 Win Mag , from difficult angles. I'm quite sure your PH will tell you the same thing.

If you will be hunting over bait, the the 458WM with the 480 gr Woodliegh will be fine! Are you takeing a smaller rifle as well, if so what is it chambered for? If it happens to be a 338 WM, 9.3X62, 9.3X74R, 416 RM or a 375 H&H, your PH may ask you to use one of those, instead of the 458WM, with the proper bullet either of those will do a yoman's job on lion. When a lion hunt these days is going for upwards of $35K, it make sense to shoot what will give you the best results. I'd sure hate to have to pay $15K trophy fee on a lion I shot, and lost!

Good luck, on your hunt! Who are you hunting with,how, and where?