And from a third Gary...
I have the ISL 370 Hp configuration (400 HP ISL block, slightly detuned to 370 HP) and roll at about 34,000 lbs plus a 4700 lb toad. I would describe the performance as "effortless" - nothing seems to phase it. Haven't climbed any really long, steep grades yet, but it handles everything else without even getting out of overdrive..
2004 American Tradition; 2014 Buick LaCRosse
Homebase in the Ocala Nat'l Forest near Ocala, FL