Kevin, I'll use 4s LiFePo, that's about 13V.
The pump itself can take revs up to 8000 (shortly) and 4000revs for a 100% running time (with HLP46 fluid). Feel free to find the data sheet for the IPZ1-HR-10 (0.6cm³/Rev)
If you know the size and efficiency of your pump you can calculate the torque it needs on the shaft:
1.59 (a fixed factor) x 0.6cm³ (amount of oil at exactly one rev) x 35 Bar (difference between input and output pressure) : 50 (efficiency) = Nm (Newtonmeter)
This torque is needed for 35 Bar at any speed! To calculate the input power for the pump you have to go this way:
Revs x Torque : 9550 (a fixed factor, also) equals Power (in Kilowatt)
Now you've to find a motor whitch generates the right amount of torque running at the right speed. My choice is a
Torcman 350-20 with 14pole and 28 windings. This company fabricates the motors in a standard program, but also they make them special to fit your project (amount of windings over 30).
Anyway, I didn't check this out yet but I believe Torcman's answers and datasheets. If I start testing the hydraulic I'll let you know and post the result.