If the wear is not even, you will have to ream the holes out so they are circular, then find and fit a bushing in. There doesn't look like there is a lot of "meat" there to ream out larger. Have you considered using silicone bronze welding wire, or rod and filling in the holes? Then drill and ream to the desired diameter, stronger than using a bushing. Running silicone bronze in a mig welder, I found it splatters less and goes on smooth if you use Tri-mix instead of straight argon, or argon/CO2. Pretty simple repair from the looks of it.