The Dodge Challenger Message Board

I would like to see what the original factory 4 speed tunnel looks like underside without the trans any pictures would be great.

You just want to see the shifter hole don't you.? Trans tunnel is the same shape as the auto, they just used a different shifter 'hump' for the 4spd which they spot welded in and filled with body filler. The auto didn't have a hump as such, but just a small raised section on the driver side where the rubber seal went around the transmission torque shaft. The auto also had a small half dimple under the auto shifter if it was floor shift. On the driver side.

I am interested in this too, anyone have any pictures?
Im looking to see how much of the floor pan needs to be cut away to make room for the 4 speed.

If you haven't done it already get the trans hump, it fits neatly around the floor pan and you can easy see where the existing tunnel has to be cut. It's not an exact science so don't fret over trimming just enough material out, I traced around the new hump (actually I made my own from some sheet metal) marked a dotted line about 2" inside the outline and then cut it out.
I installed my 4 speed with shift rods, shifter etc and then with a sharpie marked out some 'cut along the dotted lines' enough to leave about a 1" overlap, pretty straightforward

I have the AMD reproduction tunnel hump and I'm about to weld the floor back down. I was trying to figure out how much of an overlap they would have had from the factory.

One inch overlap sounds good to me.

Should I leave the section that goes over the crossmember in or trim it out as circled (red) in the attached image (from Graveyard Carz, not my own work)?

That brace is the one that the trans mount bolts up to. Chop the floor like that, you'll be ok

The shift rods in a A833 goes between the floor hump and the crossmember, IIRC.
You might want to weld a small patch to close this part of the crossmember to protect it from road grime and water (and use some rust protection for the framerails inside the crossmember, since it's currently exposed). Originally it was just left open.

Yep you remember right Fabien, I squirted filler foam into mine seemed to work ok, pulled the trans out a couple weeks back to fit a new clutch and it's still there and bone dry