I cut my 05 regular cab 2wd into a short box.
I took out 20" under door, I cut on the seam.
If you want to keep trailer hitch you will need
to cut out 2" in front of back tire on seam.
I cut 2" on rear of frame and went with a roll pan.
I cut straight down and made fish plates, 12"x6"x .375.