Under one aspect of the present invention, a liquefied gas pump assembly is coupleable to a source of liquefied gas. A cooling assembly is positioned generally adjacent to a pump module. The cooling assembly has a converging pump-head-receiving aperture, a fluid inlet line and a fluid outlet line in fluid communication with the source of liquefied gas and in fluid communication with the pump-head-receiving aperture. A pump head assembly is removably retained in the pump-head-receiving aperture so that a portion of the cooling assembly is between the pump head assembly and the pump module. The pump head assembly has a converging shape and being sized to engage the cooling assembly in a wedged configuration when the pump assembly is in an installed position in the cooling assembly. The pump head assembly has a fluid inlet pathway abutting in sealable engagement with the fluid inlet line of the cooling assembly. The pump head assembly also has a fluid outlet pathway abutting in sealable engagement with the fluid outlet line the cooling assembly, the pump head assembly being operably coupled to the pump driver of the pump module to provide a flow of the liquefied gas from the fluid inlet line, through the pump head assembly, and to the outlet line.