You can believe or not believe makes no difference to me. I had my Express on the dyno when it had a stock L31 block that had a 395' cam in it, with a tune, custom 4" air intake and shorties. I also had a 4L85E and GM 14 bolt 9.5". Not 5 minutes later a Vortec Max 6.0L went on it. The 6.0L had an intake, full exhaust including headers and a tune. The old 350 put down 310 tq at 3,100 and 257 hp at 4,900. The 6.0L put down 291 hp @ 5,400 and 299 tq at 4,400. Down at 3,000 rpm the LQ9 6.0L was nearly 50 ft/lbs off the L31. The L31 made more torque than the LQ9 over 1,000 rpm sooner, despite being less cubes and having to spin an 85E rather than a 65E. L31 was also spinning a very large duramax clutch fan and the LQ9 had factory electric fans.
Unless you don't believe GM, it's pretty well settled what the LS2, LQ9, and L31 make.