So, how does the Magnum perform and how is it holding up? Really great, according to Stephen. For example, this Magnum-equipped ’99 GMC not only ran the 2012 Ultimate Adventure, but flogged thousands of full-speed highway miles back and forth to Baja California and Washington state from Colorado without any problems. Top Truck competitor Matt Thorson runs a Magnum mid-stream between a 630hp blown LS9 and Rockwells tipped with 54-inch Baja Claws. No worries there, either. Bottom line: It looks like this Magnum beast has got real guts and could be headed for glory.