if the engine is in good condition and your getting a good price on the SC then go for it .... no way to tell you how fast it will be
with any luck it will be faster than it is now ... beyond that there is no way to tell you
Bad idea, chances r ur friend is just tryin to mak money off u or dosent kno anything about boosting cars. Ls has the low end tq that u already want, what u want now is top end power, ie turbo. if u SCed and ls teg if would be so weak at the top of the power band that a turbo ls teg would run circles around u.