LS1's however were, they were pretty underrated. They were supposedly 3-32xhp(depending on the motor) but on a ego booster dyno they could come damn close to 300 at the tire. Then again dyno numbers can be manipulated one way or another and really can't be compared. Quarter mile wise with a decent driver some have seen 13's and 107-108. Of course, QM times aren't exactly a great comparison either as there are a lot of factors with one of the biggest being driver.
Either way, the OP frumarolling is going to lose the grip advantage down low and have a good run for his money with a stock SS.