Help With Drilling Rig Project

I'm building a water well drilling rig using both new and used parts. If anyone out there has experience in that type of thing, I'd appreciate their help.

I've selected a used rotary head with a lifting capacity of 4000 kg. It comes with two hydraulic motors, 79 lmin and 48.8 cm3 each. The hydraulic pump I have in mind has a flow rate of 124 lmin at 1800 rpm and 71 cm3. There will be additional pumps to handle other functions, so this one will be devoted entirely to the rotary head.

Hydraulic fluid coming from the pump will need to pass through a control valve before reaching the rotary head. What should the flow rate and pressure rating of the valve be to enable it deliver enough fluid to the two head motors?

Mountjoy