As far as the Electrical, go with Katech they are the best. You will need the following.
Ls2 front and rear cover plates.
Ls2 vally pan
Ls2 Cam position sensor in the Ls2 front cover. Should come with one but make sure.
Use your old oil pan and windaged try if you want i did. I use all my old covers except the ones above that can not match the new 402.
I stayed with the old injectors they are easy to fit in the ls2 intake just get the Orings from Katech when you get the other stuff.
The cam postion sensor can give you a problem so make sure to get the Katech wires it is one of the best or you might be throwing the P0342 code that i did not fun.
Good luck Just pick a good engine builder it will pay off in the long run.