RV-6 info
Definitely early RV-6 wings are not swappable.
However, later ones may be. Later Phlostogen sets were match drilled to a template. My kit's splice plates were missing (some prior owner lost them... there was an estate sale involved). Phlostogen confirmed that my spars were match drilled and were able to make me a new set that fit.
As I recall they engraved a number onto the spar end, and if the number was above some value then they had been made on the jig.