lionel gp7 & gp9 shells. need help with a frame question

[the nitro man]

I'm wondering if a lionel gp7 or gp9 shell would fit on other frames such as a u36b or RS-3? They look about the same to me, but I was wondering if any of you have tryed it? I'm looking for some thing out of the normal for a lionel Western Pacific gp9 dummy. I don't want the powered & dummy to be just a like. Thanks