Power steeing issues, please help!

65 Cuda, new power steering system installed. Finally about to take car out on road for 1st time since rebuilding the entire car and the power steering basically stops and jerks at about a 1/4 turn both directions. When the car is on stands the steering turns smoothly with 3 full rotations till full stop. But when we put the car on ground with full load, the wheel only turns a bit and sounds like it does when at normal full stop and fluid leaks out the top of pump reservoir. Also now when the car is on Jack's, the wheel turns on it own to the right after we tried replacing the high pressure valve on gearbox, but also the no turn radius still present also. Any help would be so helpful and appreciated.