andre the pump is salvaged off an old loader,made by Borg Warner/Wooster,that division went out of biz many moons ago.I got it used off eBay.To replace it is about $750 USD from Surplus Center.Best guess is first section at 12gpm and second section at 4gpm.It's fed with one big inlet,1.5",feeds both pump sections.I can hit the relief valves on the loader section not too hard to do but the drive circuit just keeps going and going.It spins both axles(all 4 wheels) no problem under load(like up against a tree)The first pump section is the drive circuit..this pump section feeds the control valve,then thru a diff relief valve then to the hyd motor which is plumbed with a case drain back to the tank.The second circuit goes to the steer valve which has power beyond then on to the 3spool loader valve,then back to the tank.-Your 8gpm idea will run 4cylinders,just how fast do you want them to move? sometimes a cyl that moves too fast is hard to control.I'd go with as much HP as you can get if you're running a single stage pump.The two-section pump makes plumbing the system easy with no flow dividers or valves to slow the flow and drive up the cost.keep it simple for your first couple of projects then move up,maybe you can recylce the old parts into a new project;that's how I operate..I'm not a hydraulic prodigy,but maybe can steer ya in the right direction.