The R20Y and future pumps carried over the larger access port for plungers and springs. Minor adjustments can be seen in the bulk of the pump body, which was significantly reduced. The R20Y was fitted with both start and stop solenoids and has force-feed oil lubrication.

The R21 carried over many characteristics from previous pumps but has a different three-dimensional cam from the R20. The R22Y brought minor improvements specified for the U.S. market. Characteristics include no starting solenoid, 4mm ball thrust valves, and a different three-dimensional cam. The R23 followed the R22Y with subtle changes that improved performance. The R24Y was modified for the U.S. market. Characteristics include no start solenoid, 4mm ball thrust valves, and a different three-dimensional cam. When installed on automatic transmission vehicles the vacuum control at the venturi control unit and throttle control linkage with dead travel are eliminated. The R25 increased the number of full load adjustment notches and replaced the hex. head governor screw plug with a flange. Lastly, the R28 use a different 3D cam from its predecessors.