are these standalone gauges? anybody have a picture of the back side of them?
Yes, they are stand alone gauges. The gauges that I used and looks like Ryoken did too are Auto Meter gauges.
(The big one's aren't really 5" ones in this photo.. These were too small so I sent em back on got the 5's)
In my setup I did surface mounting on an aluminum bezel overlay that can be purchased through LMC. Here's a link for that if you're curious--
http://www.lmctruck.com/features/cc/CCBIC.htm
Unfortunately, I don't really have any photos of the back side of the setup I did, but here's the concept. You can do whatever you wish, but what most people seem to do is hack up the existing gauge cluster assembly in some way to house the new gauges. Many guys also attempt to correct the angle the gauges will face at since if you surface mount them they will tend to point down a bit. I didn't care, so I just went ahead without extensive modification to try to get the angles pointing upward better.
This pic above was major overkill, I went to the trouble of using part of the existing printed circuit to keep the function of the blinkers as is instead of using nice little green LED's like you can find at your local NAPA. (I did use a blue one in the middle as you can see from the earlier finished product pics for the high beam indicator)
And here's prior to installing the bezel over the top, and running all the wiring.
For the record, since you're inquiring about this mod, I'll add my 2 cents. This was by far one of my favorite, most appreciated mods I've done on my truck. From the standpoint of how much I enjoy looking at this every time I get behind the wheel, you just can't beat it. If you decide to do this one, you certainly won't regret it.