Can dried shrimp be used as a substitute for shrimp paste in a recipe for thai curry paste?
Your dried shrimp are fresh, then dried. The taste belachan imparts has more to do with the fact that it is fermented, than is shrimp. Fish sauce is fermented, so you really would be better off adding both :)

Rehydrating the shrimp in some fish sauce with water, then adding it to your mix for blending would work best. You may not be able to blend your paste properly if the shrimp is still dried.