Threads on a spare AC pump I have are 10-32 so I assume yours will be too.
Here is what seems a fairly scientific test of different thread repair methods:
https://www.youtube.com/watch?v=jknMrFOGMOQ
Nominal diameter of original screws is 4.82mm. It may be worth considering M5 screws and thread inserts as these are far more readily available. I would normally avoid mixing thread types but since the screws have slotted heads it will make no practical difference. There is precedent on the engine - the Solex banjo fittings are a metric fine thread.