A clamp is secured to a displacement pump, and the clamp includes an axial ring and a tightening ring. The axial ring is mounted above the tightening ring, and the axial ring is configured to align the displacement pump during mounting and to limit the stoke of a pump rod within the displacement pump. The tightening ring may be tightened such that the axial ring and the tightening ring exert a clamping force on a drive housing, which secures the displacement pump to the drive housing. The tightening ring may receive a projection extending from the drive housing to provide structural support to the drive housing.