I read on the Slant Six site that holes were cut out of the standard automatic floor pans for 4spds and a tunnel was welded in.
Four speed cars require a special floorboard hump alongside the trans tunnel to clear the shift rods and the shifter. This is because the floor shift linkage runs over the top of the torsion bar / trans mount cross member, basically through an area which is currently part of the passenger compartment of an automatic car. From the factory, these floor humps were stamped steel pieces that were welded to the regular floorboard after an appropriately sized hole (read: big) was cut out of a common floor pan.
My GTX is originally a 4spd car (broadcast sheet and fender tag D21). I thought a previous owner cut the hump to put in an auto to race the car. Now I am thinking it might be original. Has anyone seen anything this messy in an original 4spd car?