The first question is whether they're brazed or welded.
Brazed joints can be taken apart with both parts undamaged, so replacing a brazed dropout is fairly straightforward.
Welded dropouts can only be taken apart by hacksaw, so replacement must be thought about very carefully.
FWIW, I'd never consider replacing a dropout except where one is damaged on an otherwise high quality frame. An upgrade like the OP us considering makes little sense, except as a skill building exercise.
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