If He cannot get them out or you need to get another pump the choice is one form the junk yard or fixing yours. If they fix yours they are going to want to do the whole rebuild on it (they have to warrant it). A junk yard pump would be less but still cost.
There is a way to burn out the threads with a machine that used to be called I believe an EMD machine (info from about 20 years ago they most likely have something better now, updated). What the machine dose is the electrode is hollow and coolent runs through it so that it only burns in the area the electrode touches not overheating the parts around it.
The Fuel Injection Pump would need to be removed and it would be helpful to have at least 1 delivery valve holder for them see so that they do not burn down too far. You would also have to replace the delivery valves themselves if they get altered during the burning. It is a precision machine that dose the job not something hand held.
Without giving your exact address what State and City are you located in?

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84 300D, 82 Volvo 244Gl Diesel