Will the 06' SS/SC spring give me a drop on a 06' LT?

yes........................

How much of an drop?

SPRING DROPS OFF FORUM:

THEY SAY:
Rear will drop .25" to .5" -- that's all. Check CED website and get the purple tagged replacement SS springs -- they are .25" shorter then the original equipment springs. Factory original equipment SS springs have yellow tags on them.
Unless you get yourself some FE5 struts and Shocks to go with the SS/SC springs then you would get a
1.6" Front Drop and 1.3" Rear Drop. THIS IS NOT NECESSARILY TRUE

HERE IS WHAT I MEASURED:
STANDARD SS SC UNMODIFIED COBALT AT RIDE HEIGHT:
26 3/8 FRONT 27.5 REAR (TO FENDER)
GM say the ss/sc trims the car 10 mm less than the stock car. take that to the bank.

just get aftermarket springs
i got eibach sportlines and love em

The reason i want to get the ss/sc spring is to buy the struts and shocks with it because i need them. Now if i buy the struts and the springs will i need to replace the strut mount, spring seat, spring insulator, and dust shield? Where is the best place to also buy these item's if i need them?

NO you wont have to buy anything else the mount is the same. When I put on the SS/SC spring with stock shock I dropped 1" front and rear.