Repairing an old cabin pier beam foundation

[KnH]

Questions on repairing an old pier beam foundation the floor joist sit on top of the beams, the end walls are framed and sit on top of the ground.

I need to re level the whole house, replacing the bois d'arc stumps, not sure the best way to handle the end wall that sit on top of the ground.

The roof is supported by the walls that sit on the beams, the other end walls sit on the ground.
So how do I support the end walls as the floor joists are, sitting on top of the beams, the floor joists are 2x10"

[Redoverfarm]

First off I would say that this application was not the wisest building practice.  Generally all the walls to include the end walls are supposed to rest on the beams or subfloor like the sidewalls.  But given that " they are as they are" there is not much you can do other than try to rectify the situation as originally built. 

I would start off by leveling the building.  If you try to address the endwalls first then once you lift the structure you will be short on the end walls and have to address them a second time.  I would use concrete block for the beam structure if I am correct in that the original had wooden blocks ( bois d'arc stumps)  originally.

What is the makeup of the end beam structure on the ends?  Open or rim joist?  You may be able to scab onto the end sufficiently and add additional mason support blocks.  What are the condition of the base plates of the endwalls?  Most likely if ground contact they have been compromised with rot.  The end walls from what I have always been told are not actually load bearing as the sidewalls so they could be supported temporarily while you shorten and build them to sit on another foundation, beam foundation extension or stem wall (pressure treated). If you are talking 3-1/2" wall then a few 2X 's attached to the beam ends would be sufficient width to hold the wall plates.

If I have missed something bring it back with further narrative and someone might be able to give you further advice or guidance.

Without actually seeing what you have I am only able to give suggestions based on your narrative. 

[KnH]

I plan on replacing all the beams with PT lumber, some areas have failed due to rot or termites, and other areas have sunk into the soil when water leaked under the house.

If possible I want to support the end walls the same way the floor joists are, sitting on top of the side wall beams; I have read that a single floor joist or 2x floor joist can carry the end walls transferring the load to the beams? Or is it wiser to support the end walls with beams as the side walls are?

Here is a picture of one area, it's a mix of the wall sitting on the ground, beam under the wall or just cut out

[Redoverfarm]

Not real sure of what I am seeing in the picture.  Is it a floor joist that has been cut or a beam? In the sketch you indicate that you have three beams and the floor joist is resting on those but you also show large beams on the perimeter of the sidewalls.  Confusing as the joist pictured match the drawing.  Also you show the roof structure the same length as the sidewalls.  Maybe that is just the way you have it depicted but to correspond with the diagram it should be turned to match the endwall or otherwise the endwalls are with the longer portion of the cabin and not the shorter demensions.  Sorry just having a hard time visualizing.   Anyway there is no way that you will be able to have the endwalls sitting upon the floor joist unless you dismantle the endwalls and move them into the inside to set within the outer walls(side).  Maybe a couple additional photo's and explanation might help.