Can't tell without looking if yours has been modified or not, but here are a few pictures I pulled off the net that should make identification a little easier. A high hump pan is almost square in the center, rises up in front of the seat, and is always removable:

[IMG]http://img225.imageshack.us/img225/844/highhump.jpg[/IMG]

The low hump drops in front of the seat, may be removable or may be a permanent part of the floor. From all the threads I’ve read on this topic, they are not directly interchangeable, however a high hump can be added to a low hump truck if the portion from the high hump donor truck in front of the removable pan is also cut out and welded or bolted into the low hump cab.

[IMG]http://img715.imageshack.us/img715/8725/lowhump.jpg[/IMG]

[IMG]http://img834.imageshack.us/img834/1812/lowhump02.jpg[/IMG]

1960 GMC 1/2-Ton Pickup Truck
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