Case 580B Shuttle rebuild parts and method.

I am new to this forum, and I have a 1975 Case 580B that I picked up from the original owner that stated it worked when they parked it but the next year It would not go in forward or reverse. For the last 10 or so years they would only use it for two weeks out of the years to spread saw dust around the farm. They also stated that this happened about 15 years ago but they could not recall what it took to get it working again. I have been searching not only this forum but everywhere I can think of over the last three weeks to find answers to my questions to no avail. I drained the fluids and it was not milky and did not show metallic at all. Changed the filer and the filter housing was clean also. Refilled and still no movement. Went over the clutch adjustments to no avail. I pulled the power shuttle cover off and found that I had the Rockford power shuttle. The clutch discs had almost a 1/4 inch of space in them. Me being an auto and light truck mechanic for many years now assumed that I had found my problem and to the tractor apart. and started ordering parts. After getting the shuttle torn down I discovered that the clutches were like new, both steels and Frictions. They only had about 1/2 MM of wear on them. I did find that someone had been in here previously and installed the thrust bearing and washers on the forward clutch pack in the wrong order and the thrust bearing was toast. Everything else looks good and very clean inside. I have a 3-inch-thick shop manual, the parts manual and the owner’s manual for the backhoe but all it shows for the Rockford shuttle is the blow up and a parts list. No data on how much clearance the clutch pack is supposed to have and now procedures for tear down and reassembly. It does show all this information for the Twin Disc shuttle but not for the Rockford. My local Case dealer is not much help and they did some research and there are not many parts still available. A41000 force piston seals, clutch discs, and thrust bearings are about it and case makes them out of platinum or something because they are very expensive. I found Clutch discs pretty reasonable and also thrust bearings and washers at about the 1/3 the cost of Case. Looks like the only game in town for the force piston seal is case at this point. My plan at this point is to put the shuttle back together, install back in the tractor, fill it with fluid and do the pressure tests. Which I should have done before I split it. My questions are these: 1. How much shuttle clutch disc clearance is acceptable? Or where can I find this information? 2. Is there a tear down and reassembly procedure available somewhere 3. How is the shim pack thickness determined at the shuttle to transmission shaft for reassembly? 4. I have read several threads about a pickup screen that can get clogged, but I do not see any pickup tube or screen on my tractor. Is this something that was in the early 580s but not on the later ones? If mine does have one where do I find it and where do I drill the access hole so I can service it? 5. I have the sizes for the force piston seals but the small of the two is a flat O ring. Does anyone know where to look for a 5 3/8 ID flat o ring?