Hi,
Wow, rear rail sag without evidence of fracturing ? well that's a new one to me. Normally when a rail has sagged it will have a fracture in the vertical section of the rail, but I will say with those shots you provided it looks pretty good. I guess you'll have to strip more paint around the engine mount area so as to reveal what's really going on. If nothing then you are going to require the services of a press and reverse the bending process. One thing that I must stress and that is the bed knife will have to remain in the chassis when doing this procedure as it will hold the chassis rigid and stop the side plates from folding inwards.
To remove those screws one has to use the exact size screwdriver that completely fills the slot and then with solid downward force tap the back of the screwdriver while applying a twisting force. The impact will shock the screw loose.
You really don't want to bugger up a carrier as they can be quite expensive to replace, depending from where you buy it from.
Cheers,
BB.
