An assembly comprising: a block having a first end face, a second end face opposite the first end face, and a plurality of through-holes (208A-D) extending between the first end face and the second end face; a first clamp plate and a second clamp plate, each clamp plate having a respective plurality of through-holes (214A-D; 216A-D) corresponding to, and aligned with, the plurality of through-holes of the block; a first set of fittings, each fitting (220; 600) of the first set of fittings having a first end inserted through a respective through-hole in the first clamp plate and the first end face to be received within a corresponding through-hole in the block, wherein each fitting has a second end opposite the first end and configured to couple to a tube; and a second set of fittings, each fitting (230; 600) of the second set of fittings having a respective first end inserted through a respective through-hole in the second clamp plate and the second end face to be received within the corresponding through-hole in the block, wherein each fitting has a respective second end opposite the respective first end and configured to couple to a respective tube; wherein each fitting of the first set of fittings and the second set of fittings has (i) a first annular groove disposed in an exterior peripheral surface thereof, and (ii) a second annular groove disposed on the exterior peripheral surface and spaced axially apart from the first annular groove, wherein a radial seal (244; 608) is disposed in the first annular groove within the corresponding through-hole in the block, and wherein a retaining ring (246; 602) is disposed in the second annular groove, such that the retaining ring is disposed between a respective clamp plate of the first or second clamp plate and a respective end face of the first or second end face of the block. a block having a first end face, a second end face opposite the first end face, and a plurality of through-holes (208A-D) extending between the first end face and the second end face; a first clamp plate and a second clamp plate, each clamp plate having a respective plurality of through-holes (214A-D; 216A-D) corresponding to, and aligned with, the plurality of through-holes of the block; a first set of fittings, each fitting (220; 600) of the first set of fittings having a first end inserted through a respective through-hole in the first clamp plate and the first end face to be received within a corresponding through-hole in the block, wherein each fitting has a second end opposite the first end and configured to couple to a tube; and a second set of fittings, each fitting (230; 600) of the second set of fittings having a respective first end inserted through a respective through-hole in the second clamp plate and the second end face to be received within the corresponding through-hole in the block, wherein each fitting has a respective second end opposite the respective first end and configured to couple to a respective tube; wherein each fitting of the first set of fittings and the second set of fittings has (i) a first annular groove disposed in an exterior peripheral surface thereof, and (ii) a second annular groove disposed on the exterior peripheral surface and spaced axially apart from the first annular groove, wherein a radial seal (244; 608) is disposed in the first annular groove within the corresponding through-hole in the block, and wherein a retaining ring (246; 602) is disposed in the second annular groove, such that the retaining ring is disposed between a respective clamp plate of the first or second clamp plate and a respective end face of the first or second end face of the block.