Nitrous with mainly stock LS1?
you should be good up to a 150...but at that power level i would be looking into upgrading your fuel system (pump and injectors). also a good dyno tune would be a must so your tuner can pull some timing and get your A/F spot on. as far as hardware, i'd start with a wet kit from one of the sponsors, and add a window switch, fuel pressure safety switch and a few other gadgets. im pretty new to nitrous but thats how i approached my dry kit. the vets will have plenty more to say but thats it in a nutshell. 
You may be able to run a 150 wet shot with your mods. You should probably take it to a dyno and start out with 75-100 shot jets and see where the a/f is at. Sometimes if I do up the jets I may throw in like 150 nitrous and 175 fuel this way atleast it should be alittle rich instead of lean and if it seems like you can lean it then do 150 nitrous and 150 fuel. If you plan on running a dry kit im pretty sure your going to need injectors btw what kit do you plan on running because some are rwhp jetting plus the nozzle flows better on some kits yielding higher numbers.
