LS Truck Block Drill Template to Mount Alternator LS1 LSX 551445 LS Truck Block To Mount LS1 Alternator (Low Mount) Billet Aluminum Have an LS truck block and need the second mounting hole for low mount alternators or other accessories? Just attcah the template with factory hardware, mark the hole, then drill the hole with an "R" drill bit (.339" or 55/64"), then use an M10-1.5 tap. (This is in a non critical part of the engine block.)