[lisa]

Select the appropriate faces in the texture coordinate editor, then click "Flip Horizontal" or "Flip Vertical" depending on how they are oriented. Scoot them so the edges line up to their matching half. Then select everything and resize to Max to fit it all to the UV map.

Since you have two distinct object, you will likely get some polygons stretching between the two when you import into SL, as SL always imports as one contiguous shape.