I just bought one of these fancy fandangled things, but it apparently comes with a knock sensor, where aboots would one put a aftermarket knock sensor on a LS?

 

Is it threaded like a bolt? Or has a way to fasten it with a bolt?
Find a tapped hole on the side or top of the block that you can use.

 

Did you get a PLEX?

It's been a while since I've used one, but IIRC their instructions are pretty good about explaining the different locations then "tuning" the software.

 

I bought the ICT aluminum blocks and the extension wiring harness which those aluminum blocks bolt to the side of the engine by the motor mounts in pre drilled holes and you bolt those into the block on each side, and then screw your knock sensors into those blocks and connect the harnesses to each one and just make sure your wires dont touch your headers and you are good to go. If you are on a budget, you do NOT need to buy the ICT Brand blocks and can get an imported one from Amazon for about half or one third the cost, and I thought the ICT came with the extension harness but it does NOT! Don't make the same mistake I did and spend more than you need to. You do not need any funky sensors, stock ones work with this setup you can see them here.........
go to www.amazon.com and search this........

knock sensor extension harness

Knock Sensor relocation kit

You will get a few companies aluminum blocks and a few extension harnesses. Overall, fairly inexpensive and you will need a new valley pan because you wont need the one with the 2 huge holes in it with the tar all over it. I bought an ICT polished plate and it arrived and it was far from "polished" so I did the Sanding of it from 400 grit through 5000 grit then used the Brown tripoli, then Green cutting and then white jewlers rouges on my hand grinder with the polishing wheels and now its a mirror with optical clarity to reflect the digital LED lights I have under my intake manifold to add a little spice under my hood. But overall this relocation kit from the few companies are all pretty much the same from what I can tell. THey are a great way to clean up your engine bay if you want a nice clean engine compartment without wires laying all over the place and some shiny parts in there. Some are into the clean asthetic, some could care less. I like the show stuff as well as the go stuff.
SOme folks opt for tuning out the knock sensors, I personally think they prevent some bad crap from happening so I made sure I kept mine in the tune and relocating them has nothing to do with any tune, so you dont have to send your computer out if you relocate them. Engine does not care if it gets a knock signal from the valley pan or the outside edge of the block, its all the same to the computer. I would think the sensors would be more sensitive on the outside but thats just a guess.
Hope this helps you some
J