Buckets into Factory Bench Car

IDK about later vehicles but every bucket seat 65 Dart, Valiant and 65/66 Barracuda I’ve ever parted out had them tack welded on top. I agree they would be better suited underneath
the 67 up are on top too. There are cross members underneath in places so maybe that's why they are on top? or just easier for the factory to install after the fact. ( since all the bench seat holes are punched and the bucket seat holes are not in a bench seat car they were probably added as needed)