Just tried a used snug top shell reportedly from 05 tundra crew cab that did not fit my 05 tundra extended cab.
The camper store dealer said that they where the same bed. Installation seemed to take a long time and when they brought the truck out, the dang thing didn't fit and was scratching the outside of the bed where the front corners of the shell were resting just below the rails, so I made them take it off.
Does any one know; What are the outside dimensions of the bed on a crew cab v/s extended cab?

First, there is no such thing as a Tundra crew cab or an extended cab ( at least for the 1G).

There is an ACCESS CAB and a DOUBLE CAB.

The bed size is a bit different in 2 respects:

1. the Access Cab is about 1/2 inch longer

2. the Double cab is a few inches Higher ( deeper) which will not affect the installation of a camper shell.

As far as interchangeability, I have installed the same camper shell on a double cab and on an access cab with no problem. You can always slide the shell forward or backward a bit to get closer to the cab or perfectly fit to the tailgate. In fact I sold one and installed it on an old Toyota T 100 with no problem.

I think what your seller had a shell from another truck ( Ford or Dodge ) and it will never fit any Tundra.

Same here,

I took my 02 Access cab leer shell.......painted it and dropped it on a 06 DC bed

Had to slide it back a bit so it would not rub the back cab when hitting bumps....so it sticks out a bit in the rear about an inch or so ......
added some thick weatherstripping to the bottom of the back Shell window to take up the air gap and help keep the dust and dirt from being sucked in while driving......

They are just not the same length and the angle of the back of the cab is also different. I had to get a new shell going from my 03 Access Cab to my 05 Double Cab.

Depends on who makes the shell

my LEER fits both AC and DC

Glad everyone got a camper but really what are the dimensions that I measure to fit one on my 2005 Tundra Double cab?