I have started a new project and one of the first things I am going to do is replace the floor pan. With this in mind, I will probably replace the Turbo 350 with a 700R4. I thought I read someplace, but I can't find it again, that the transmission tunnel will have to be modified for the 700R4. If so I want to make the changes as I put in the new floor plan. Can someone confirm weather or not the tunnel has to be modified?

No mods required.

Ditto

Even a 4L80E fits beautifully under a 1st Gen F body. :)

Great news! It sounds like my plan won't be a big deal to do. Thanks for the help.