Maybe it's just an artifact of the camera, or the way the light is hitting (and I am definitely no expert), but the riveting looks weird to me, like maybe the dimples were slightly too big, and therefore the rivets a little too countersunk? They also have a look like they were set with something smaller than the rivet head itself, and have a little cup in each one, but again maybe it's the lighting or camera angle.
Otherwise, looks like things have been stored in a barn type area, which may be good or bad, but if there has been rats, mice, or cats running around, I would look over everything very carefully for any signs of pee damage. I can't tell on the empennage attach area, but it looks like maybe some corrosion or graininess happening under the primer or whatever is on that area?
Also, check for any SBs, for example looks like you need the gusset reinforcements on the engine mount/gear leg, but that should not be a big deal since there is no engine yet.
Otherwise, on a -6, the hardest thing to tell from pictures is how square everything is. My understanding is that it required the builder to to build a square jig first, and then build the plane to that. If the jig wasn't square, or the builder not careful, they can be pretty lopsided and there really isn't any way to fix it once certain holes are drilled and riveted.
An RV-6 is still the most economical of all the RV's, and the best bang for the buck, but they are from a time (mostly) when it was more hard core building and not just assembly of pre-formed/punched parts, so the quality variation between each builder is bigger than the later models.
Again, I am no expert, so if you have someone that knows that can put eyes and hands on it, way better than doing Bladerunner on the pictures.