Rear axle at the spring mount. This works for pretty much any medium duty or heavy duty truck. If you want to lift the weight off the springs, you would lift the chassis frame rail, preferably close to a spring mount.
Front swing arms, on my 2003 chassis there is a round boss on arm near the wheel, but there is a specific jack (we don't get with a motorhome) that cradles the boss. For a bottle jack with a flat top I would lift the bottom surface of the arm close to the location of the boss. Yours is the previous generation, but I think the front suspension was essentially unchanged.
Tom Test
Itasca Spirit 29B