I found it!
Another way to cut pumping cost which would be easier to control follows. I would use a 16S05-5 pump end, remove 2 impellers, and use a 1/3 HP motor. This pump would deliver 16 GPM at 50' of lift. Control this well pump with a 20 PSI Cycle Stop Valve, a small pressure tank, and a 10/30 pressure switch. After the pressure tank, one line tees off to the heat pump, another tees off to a booster pump for the house. Use about a 3/4 HP jet pump with it's own Cycle Stop Valve set at 50 PSI, and a 40/60 pressure switch.
When the heat pump alone is running, an electric discharge valve opens, the pressure tank drains to 10 PSI, and the pump starts. The 20 PSI CSV will vary the flow to match the 12 GPM usage and maintain 20 PSI. This should cut your pumping cost to 1/3 of what the 3/4 HP is doing now. When the heat pump shuts off, the electric discharge valve closes, and the CSV slowly fills the pressure tank to 30 PSI, and the well pump is shut off.
When the house alone is using water, the pressure will drop from 60 to 40 PSI and the 3/4 HP jet pump will start. The 50 PSI CSV will maintain 50 PSI to the house no mater the flow rate being used. This jet pump system is drawing water from the well pump system, so the pressure tank on the well pump system empties as the pressure drops from 30 to 10 PSI, and the well pump is started. The CSV on the well pump feeds exactly as much water to the jet pump booster as the house is using. Both pumps run as long as the house is using water. When the house stops using water, the CSV on the jet pump will slowly fill the pressure tank to 60 PSI, and the jet pump is shut off. Then the CSV on the well pump will slowly fill it's pressure tank to 30 PSI, and the well pump is shut off.
When the heat pump is running, the well pump/CSV is delivering 12 GPM at 20 PSI. If the house needs water at the same time, the jet booster pump comes on, and the CSV on the well pump opens up to supply both the heat pump and the jet booster pump. Depending on the water level, you should be able to get about 18 GPM total when the house and heat pump need water at the same time. When the house no longer needs water, the jet pump system will fill it's pressure tank to 60 PSI, and the jet pump is shut off. Then the CSV on the well pump reduces the flow to 12 GPM, matching the amount used by the heat pump. Again, when the heat pump is shut off, the well pump fills it's pressure tank to 30 PSI, and both pumps stay shut off until water is needed again.
If the water level in the well pulls down to more than 20' at high flow, you will have to stay with a ½ HP well pump and not remove impellers from the 16S05-5. Even this will cut your pumping cost to half of what they are now.