Alright, got some numbers for ya.

I wasn't quite sure how you want the dimensions, so I've modded your picture to illustrate where I measured from. I also added a dimension for the thickness of each cab's floor section as they vary quite a bit. "E" will be the extra dimension. Lastly, the seats on all but one slant towards the back, so I'm including dimensions for seat height at the front and back edges of the seat.
First cab is a RoadBlasters sitdown. The monitor it uses is a 19" oriented horizontally.
A: 13" at the front, 11" at the back.
B: 20"
C: 19"
D: 24"
E: 4.5"
Next cab is a Spy Hunter sitdown. It uses a 19" monitor oriented vertically.
A: 12"
B: 26"
C: 24"
D: 42"
E: 8"
Third cab is a Hard Drivin' Deluxe sitdown. It uses a 25" monitor oriented horizontally.
A: 12" at the front, ~8" at the back.
B: ~36" The seat in this cab is mounted on a swing arm with a lot of front to back travel.
C: 24"
D: 28"
E: 7"
Last sitdown is a Namco Air Combat. It uses a 52" projection TV for a monitor.
A: 9" at the front, 7" at the back.
B: 23"
C: 13" (Flight sim cab, controller is a center mounted joystick.)
D: 32"
E: 11.5"