I don't know where they exist online but my paper spec for the 2001 RAM (same as the 2002 2500) has some numbers:
depth of box - 19. 4"
width between wheelhouse - 49. 9"
tailgate opening - 62. 9" (but the space between the sides is really 60. 5")
tailgate load height (4x4) - 37. 1"
tailgate load height (4x2) - 33. 7"
There's more if you need them.
Getting closer, but can't get the 6. 7 into the specs.I found these Car & Driver RAM 2500 specs
Be sure to pick the right body style and drive train to get the right load height.