Many years ago I became a Gold Member at TrainzItalia, at that time the Huge Boys were offered along with a few other American locomotives. #8003 came in huge_boy_8003.zip dated 4/19/2013 and contained Huge_Boy_8003.cdp dated 1/14/2008#8000 is contained in UP8000_Huge_Boy_v2.cdp dated 9/30/2007
I am not authorized to distribute these assets and your best bet would be to take up UP844 on his very generous offer.