If you have access to a lathe then you can buy whatever die you want and modify it accordingly, however if you don't buy the RCBS 500 S&W dies. They don't require any metal to be removed.

Also call up RCBS and buy a 50AE expander die. If you don't AND you don't ream your cases you will buckle the case in the middle as the 500 S&W expander is just a touch too large for a non-reamed 500 JRH case.