I would suggest a 6.5x68 and a .375x68 would be a very good choice.
The .375x68 is simply the 8x68 necked up to hold a .375" bullet. I made this wildcat many years ago, in the 1990's. I shot it a lot, then sold it to my buddy Keith, who shot it a lot, then sold it to his brother who did the same, then rebarreled to the same chamber by Huntington's in the States & gave me the original, worn out barrel back. It easily exceeded the .375 H&H due to having 3 or 4gr. greater capacity. This was the third ctg. rifle combination I converted rifle ctg. cases into bullets for.
The other two were a .458 2" and a .358 Norma mag.