if you have not got the old bits out, then drill the back of the carrier in line with the pins with a bigger drill than the pin and try to drift them out, if this does not work then using the slider hole revealed with a drill that fits, drill the pins out from the back, it is important to keep the drill aligned as the cast is easier to drill than the steel pin and it will wander if not controlled carefully, if you are not confident with that then after marking the center with the bigger drill go down a few sizes and drill the entire pin, if it comes out full centre on the broken side then you should have no trouble drilling full size, if it is to one side then drill progressively bigger till the emerging drill just touches the side of the cast, then there should be insufficient metal of the pin to hold it in place and the remainder should drift out leaving an undamaged hole, Rick