I think most poeple don,t try hard enough with their 458s , as mine have been very accurate !
The old Ruger I have now will easy put 3 shots in the same hole ( Ok large hole )at a 100 yards !
I,ve shot a fair few Crocs , I don,t think you need to be more than 100 yards away - 75 yds will be a long way , yes brain is walnut size ,but any where near it will stop him till you get there ( shock inside skull,it,s all bone ) & you have a margain with 45 Cal , also you can break both shoulders which kills and stops most times & skull is undamaged ( make sure he is well up bank faceing toward land ) the 458 Win will do it all , just shoot your rifle a bit more !