A method of manufacturing a plurality of housings. The method may include maintaining an inventory of initial products. Each of the initial products may include a central hollow body extending along a longitudinal axis and monolithically formed with at least one of a suction passage and a discharge passage. Each of the products may have a same initial length. The method may further include receiving a first order for a first housing having a first length and machining a first product to the first length to form the first housing. Also, the method may include receiving a second order for a second housing having a second length and machining a second product to the second length to form the second housing. The first length and the second length may be different.