You are correct, the camshaft is slightly different as well(but most ppl want to change the cam completely anyhow). The LS1 motor is definately underrated by GM. As an example, me and about 25 other guys dynoed our cars at once. The stock LT1 cars dynoed at around 240 rear wheel hp(15% drivetrain loss), which puts it right around 280hp at the motor(rated at 275). All the stock LS1 cars where dynoing around 300rwhp, which computes to around 350hp at the motor!!! These cars are only rated at 305hp at the motor! Incidentally, my car dynoed at a max of 282rwhp @ 5300 and 315rw ft/lbs torque @ 2500, which computes to around 330hp/370tq at the motor(around 55hp added with mods).
Hey, for anyone who is interested, I found a pic of the infamous 725hp ZL-1:
BTW TNproud2b, you live in Tennessee...Isn't there a law down there that you have to have either any American pickup truck or any car ever made into a NASCAR racer? Where do you get off driving a Jaguar in Tennessee?