A belt conveyor (100) for an agricultural harvester comprises first and second conveyors that include side rails (102, 104, 120, 122) made of extrusions in which the side rails (102, 104) of the first conveyor have extruded profiles that engage extruded profiles of the side rails (120, 122) of the second conveyor (130), wherein the mating extruded profiles permit relative sliding movement between the first and second conveyors. The two mating pairs of side rails (102, 120 and 104, 122) may be driven in parallel by a common motor (706).