The bore for a 60mm roller bearing is going to be 68mm from memory. A babbit bearing bore will be around 63mm. Obviously a 55mm babbit bore will be smaller, but I don't believe Cam cores to be as plentiful. If you have to replace the camshaft as well, this might be the best option??

Alternatively, you can sleeve the number 3, 4 and 5 bores to facilitate the repair. Maybe pin them with some aluminium rod to minimise the possibility of the sleeves moving.