I want to use this switch for a blue light. has anyone used one for this perpuse and does anyone know where i can find all the leads for this circuit

On an ext cab, you will find the leads in the roof towards the center. You will have to pull the headliner on the driver side and kind of fish them out. 2 wires iirc, brown and black.

That being said, I would just go into the panel behind the driver's side rear door and find the relay and tap off the brown and black off of that. You should hear the relay click when you push the switch and it'll help with the location. The circuit is good for 10 amps so LED's should be OK but strobes will be a little too much.

is it beind the seat on the ext cab

I believe it's right near the corner where the hinge for the rear door is. Fold up the back seat and start peeling the trim away.

i got it. i took the seat out it was pretty easy. it is nice for the whelen power pack I am using

2 wires iirc, brown and black.

That being said, I would just go into the panel behind the driver's side rear door and find the relay and tap off the brown and black off of that. You should hear the relay click when you push the switch and it'll help with the location. The circuit is good for 10 amps so LED's should be OK but strobes will be a little too much.

How many amps is this circuit rated for?
Looking in the manual for my 2002, the relay contacts are powered +12V from STUD 2 Max 1 30A fuse, (located in Fuse Block Underhood), if you have the 5X7 option, or it's powered from SEO 2 Fuse 30A if you have the TRW option. Not sure about your 2005.
The relay coil is powered from SEO 1 Fuse 15A.
Reference Helms 2002, pages 8-311 and 8-313.