Is the barrel to the original sporter taper or are you putting it back to the MBL configuration?
I believe that most of the .461 sporters had either a one standing/one folding or perhaps a one standing/two folding rear sight. It was more common for the smallbore rifles to have more leaves although the .461 is quite capable of reaching out to a pretty good distance sighted as an MBL or match rifle.
If you need measurements from mine let me know.