FRH,
My first concern is why are the pumps failing? Is the oil dirty, full of water, relief valve set incorrectly, something plumbed incorrectly, etc.
With a little work you should be able to find a replacement pump for your Jinma
Critical items are:
Rotation as viewed while looking at the input shaft
Pump mount pilot diameter Typically these are made to some standard
Drive shaft diameter and if splined number of splines
Drive shaft exposed length typically these are also made to some standard
Displacement: this may be the hard part. If you know the published flow for your tractor then it can be calculated most newer pumps will be rated in cubic centimeter per revolution
Port style and location if Lines to pump are hoses then this is not as critical
Pressure rating: rated for tractors required operating pressure
There are several companies that make quality pumps.
A few of them are: Danfoss- Turolla, Marzocchi, Parker, Rexroth, Etc.