Sort of a different hump question

[va944]

My 61 Suburban came with a high hump trans cover but based on other things I am finding I don't trust that it came from factory that way. In digging into it it does not seem to fit right in picture you can see that it does not follow contour of floor pan. Can anyone tell me what if anything is wrong here? Floor pan does seem to be original. I also was hoping someone could tell me how the upper trains hump is supposed to be attached to the firewall previous owner had pop riveted. As always thanks