A drive system for a cryogenic pump is provided including a spool housing having a plurality of valves disposed therein about a pump axis and a tappet housing including a plurality of tappet bores, each tappet bore in communication with a respective one of the plurality of valves. A collection cavity collects hydraulic fluid from the tappet bores. A pump flange includes a fluid inlet and a fluid outlet. An inlet manifold directs hydraulic fluid received through the fluid inlet to each of the plurality of valves. An outlet manifold directs hydraulic fluid from each of the valves and the collection cavity to the fluid outlet.