These holes afford several inches of forward/rearward adjustment of the seat. This would hardly be a quick change, as one would need to remove the seat from the side mounts to even get to the bolts holding the side mounts to the seat frame. That being said, it is possible.
They do so many seat installs on race cars that RRE decided to simply CNC machine threaded weldable inserts. Since the steel tube doesn’t have a lot of wall thickness, trying to tap and thread the holes won’t really work, and wouldn’t be particularly safe, either. These weldable inserts allow for a ton of thread engagement and strength for securing the seat brackets to the frame.
You can see that our placement is slightly misaligned from the original holes. Either my body is crooked, I like sitting crooked, or perhaps I was sitting crooked previously. I never noticed it, and the new measurements seem to indicate the mark is more or less parallel to the chassis frame rail, so whatever.
Then again, perhaps the whole car is crooked. Not impossible.