So I proceeded to take the cover off and with it came a bunch of roller pins and broken rollers.   My first thought was that I would take the pump out to see the lobes on the shaft all screwed up as well, but when I pulled the pump down, the lobes look perfect.   There is a little rust on two of them but feeling around on them with my fingers they feel just fine.  

Here's the pump.  As you can see two of the rollers are gone, and the third one the pivot arm is half broke, and the fourth one is lodged in towards the pump.

Here is a picture of the lobes on the shaft in the tractor.   They all look and feel good.   There is a bit of rust on two of them, but this tractor sat for some time and who knows how long ago this pump went atomic.  And what would cause all of these parts to let loose, low fluid level?    

So is it possible to find the parts I need and fix this pump or am I better off looking for another one.  And was this style pump unique to the D19's or was it the same as some of the earlier D17's.  It would be nice to get it back together so the rear lift works on it.   I know this hydraulic system is no where near as good as a front pump system but all I'm looking to do is use the rear lift and possibly a cylinder on a haybine/baler etc. so this system if working will be fine.