Snook, have you considered there were no 30-06s around during the time the great buffalo herds were slaughtered?
A large, heavy LEAD conical will do an exceptional job of killing even at extended ranges when powered by only 70 or 80 grains of powder. Some of the better designed lighter bullets used in sabots will do NEARLY as well.
Might I suggest that you get the performance of your '06 detached from your thinking so far as entering into muzzleloading. Unless you want to go with one of the few smokeless choices - you are not even close to being in the samearena with the centerfires.
I suggested a combination of rifle and components that will probably get you about as much as you can get so far as range and performance, short of going smokeless.
Or, you could buy a nice White and do it right.
take note of this group
what isn't shown in the above is that point of impact was 32" below point of aim. A very consistent 32" below point of aim and plenty of power left to kill a buffalo, perhaps an elephant.But you would need to learn a whole lot more to deliver that load accurately than you would with your 165 grain '06.