MC on the left is for a power booster. The MC on the right is for manual brakes. Some aftermarket companies sell the MC with deep hole for both applications. They supply you with a pin to place in the deep hole if you are using it with a power booster. For manual brakes you leave the pin out.
In other words, you can use your old master by making a pin, but you must check the clearance, just as you would for even a direct replacement.
Many times, they use a MC with larger diameter piston when mated to a power booster.