A modular printhead assembly facilitates the manufacture of printers with print zones of differing widths. The printhead assembly includes a pair of end pieces and a plurality of rods that extend between the end pieces in parallel. The rods pass through holes in lugs extending from carriers configured for the mounting of printheads. Plates are interposed between the printheads and the carriers to enable actuators to move the plates and printheads within the perimeters of the carriers to adjust the stitch and roll alignments of the printheads.