In one of the multitude of gas vs diesel threads, it was mentioned that Navistar now had gas engines, which I hadn't heard before.
A quick search turned up an article about a purpose built version for school buses. Apparently, they have had a propane version for a while so they changed to gas and adjusted the power curve for school bus use, I would assume.
, PSI's purpose-built 8.8-liter model. Like its propane-powered counterpart, the highly efficient gasoline engine provides diesel-like performance—rated at 265 horsepower at 2800 rpm and 545 lb-ft of torque at 1800 rpm