The challenge for epoxy will be those drill craters having been exposed to oil residue for probably extended period. Hard to know the penetration depth but oils & similar residues are a natural releasing agent for epoxies. It will make bonding challenging. You might have to soak it in some aggressive solvent & maybe even grind the divots with a burr to give the resin some mechanical tooth. People seem to have good results with those rust removal liquids & I think some other kind of treatment to stop further oxidization. You can get pigments & powders to add the resin that might make it a closer match to the metal. But I'm guessing you want to make it nicer looking, serviceable & less abused. You could try a crater with JB Weld & just see how it goes. If its horrible, its easy to grind out & you are back at the beginning.
On the metal side I've seen some neat TIG brazing videos which might be lower distortion heat. But the alloy will look quite different than the cast iron. I think it would be a more solid solution
The other thought - more risky of a total loss. Mill out the offending area, screw/pin in a new slab of CI with high quality retaining adhesive & mill it to conform. Really depends on how deep the over drills are, how much meat is left, whether the loss of material will cause any warp, how accurately you can resurface the mating parts especially if it sliding on a dovetail vs 90-deg edge I cant quite see there. I have seen some beautiful fixits where people drilled out a broken tap & inserted a plug of native material & you would never be the wiser if the line wasn't shown under magnification.
n.
