you can always re tap it bigger and get the bolts to fit. a tap and 3 bolts will cost $10 and then a gasket will be about $7. you would need to drill out the head and maybe the gasket but if you are carefully its very much achievable. ive done it a few times with the bits and pieces sitting around and it works as good as the heli-coils or similar. i would recommend going a courser thread metric tho because it only aluminium and a fine thread would be harder to tap and probably end up less durable because its easier to cross thread a mild steel bolt in a fine thread aluminium then a course thread.
regards jay
