You should be able to get a reamer maker, maybe Pacific, to come up with a chambering reamer with a .460 shoulder and .470" base, for the neck already in the case(if the bored is OK). Such a reamer could be hand fed for perfect results, as it would only be 'cleaning up' the back end of the chamber.
After that, any .30/06 based brass could be used, or even 7 or 8x57 Mauser brass - neck it straight, then neck to hold a bullet putting the shoulder where it should be, then FF.

The .005" taper per side is fine as it worked perfectly on my .375/06IMP round. I am running quite high pressures, I assume as I am getting 2,650fps with 270gr. TSX from it's 26" bl. Extraction is accomplished with little finger bolt lift and extraction.