A pump features a motor, a pump head (PH) and a locking pin (LP) that are uniquely coupled together. The motor has a front end bell (FEB) with a FEB coupling portion configured with twist lock style (TLS) connections with locking portions, and an outer surface with a detent. The PH has a PH portion with a PH coupling portion configured with corresponding TLS connections with corresponding locking portions, each having a locking stop, the PH portion has an outer surface having a threaded orifice. The LP has a threaded portion and an end portion, threads into the threaded orifice and engages the detent after assembly of the motor and PH. Each corresponding TLS connection couples to a respective TLS connection when the FEB coupling portion and the PH coupling portion is pushed together. Each locking portion engages a respective corresponding locking portion when the FEB coupling portion, and the PH coupling portion is twisted together in relation to one another about the longitudinal axis of the pump. Each locking stop abuts against a respective locking portion to stop the FEB coupling portion and the PH coupling portion from twisting together, so the detent and the threaded orifice are aligned to receive the LP, and the motor and pump head are locked together and cannot be pulled apart.