It's not similar its the same. A 5.3 or 6.0 is exactly the same as an LS1 as far as sensors and demensions go.
As for the LT1 to LS1 conversion, the engine mounts are different, the trans bell pattern is different (not entirely different but not all bolts match up), the torque converter pilot and bolt circle is different, the wiring is different, the radiator is different (but can be made to work), and I'm sure a dozen other things I'm not thinking of at the moment.
The easiest way to perform a swap like this is to get an entire dropout from a truck or f-body so you have the wiring harness, engine, transmission, PCM, MAF, and then you'll either need conversion mounts or a different k-member. To be honest I'm really not sure what you'd get into making the gauges and such work. The accesories would need to be off an LS1 f-body (I suppose GTO or Vette accesories would work but the truck accesories interfere with the car intake manifold you would need to clear the hood and cowl). There is basically nothing about the LS that is the same as an LT1 when it comes to reusing anything.
Anything specific you'd like to know after reading up I'd be happy to try and answer it since I know the LS1 f-body platform pretty well.