From what I've seen, the Second Gen Camaros did not use the 12378 on the cowl tag. Only the VIN differentiated between the V8 model 12487, and the 6 cylinder model 12387. I believe that the 12487 on the cowl tag indicates only Camaro Sport Coupe body.
Earlier GM cars had the same numbers on the cowl tags and the VIN tags for this part of the model.
However, we know it shouldn't be a 6 cylinder model by the TH350 tranny, unless that has been switched out. A 6 cylinder should have originally had a Powerglide tranny.