I believe a WS6/TA Has like 325HP. and runs like high 12's low 13's (I think) And plus they have very good suspension/weight transfer. Even with those mods your hp is not equal with the ws6. And I think the ws6 comes stock with like 3.42's or 3.73's (I am not sure just heard) But I wish it was that easy =)
I think they have 323's from the factory.
Factory freaks are dyno'ing 320-330 but I believe more are in the lower 300's.
I may be wrong though. They do take well to simple bolt-ons that Mustangs don't shine as much with, for example a lid. They're netting about 10 hp with just that which is the same thing as a cold air intake for a Mustang. Cutouts are also giving them a few ponies and torque. Long tubes really do wonders on an LS1 as well !