[hatzie]

The fact that they wouldn't sell em to the public has more to do with Tioga, Broome, Chemung, Chenango, Otsego, and Delaware county politics mixed with the NYC moonbat driven BS from the Assembly, Senate, and Governors office in Albany. Every time I see this BS I think how glad I am that I left the area 37 years ago.
Combine that with the bizarre Carnie mentality you see in flea market sellers and junk car outfits. They'll get pennies on the dollar or nothing at all by scrapping them or pitching them in a dumpster rather than sell them for less than they think they're worth.

The 6.0 has more HP and Torque than a stock carbureted 454. Around the same power numbers as a GMT400 with a 454 TBI... Significantly more HP and slightly lower torque to the 6.0L LQ4 compared to the 454 TBI. The 6.0L LQ4 definitely gets better fuel mileage than a square or GMT400 with the 454.
My best mileage in my 86 K20 with a 454 and 700R4 was 9.5mpg on the highway. I get right around 14 with the 6.0L K2500HD. The 2500HD is a heavier chassis with the same gearing as the old K20 squarebody.
My best in-town with that 454 K20 was 7mpg. The 6.0 gets just shy of 12mpg but as low as 11.

The numbers on the VVT version of the 6.0L truck motor in the GMT900 and newer rigs moves significantly in the favor of the 6.0L over the old inefficient 454.

The 325ci 5.3L has more power on tap than the 350 smallblock. The 4.8L LS V8 has better numbers as well. Even in the heavy GMT800 & GMT900 chassis they pull fairly well.

The electrical and mechanical engineers beat the bean counters on the LS.