What is the correct position for the heat shield on the firewall for a 1913 Runabout ?
It goes on the firewall. There's only one place it will fit. If everything is right it just clears the steering column and it just clears the head bolts.
There are some not so good reproductions out there that are not made right. If you get the one from Fun Projects it is just exactly like the originals and comes with proper attaching hardware.
Note that the floorboard in the photo was cut out because the car used to have a 1925 engine. A high later head won't clear the floor board in a '13.
Royce has his in the right place, but I don't think it is an original heat shield. John Regan makes exact copies of them. They pretty much change the design every year except 13-14.