I purchased the jack pads from Amazon. They are called Quality Plastics Utility Block and come in a four pack. You can also find them at the northerntool.com website.
They are a bit pricey, but I have seen the less expensive blocks crush under an RV's tires so decided to go with these.
As for the propane line running down the passenger side of the frame, I removed the bracket that was holding the line in place where I wanted to mount the jack. I then used a large screwdriver to lever the line slightly inward of the frame while I mounted the jack. I then placed a small piece of heavy-duty rubber between the jack and the line to prevent metal on metal rubbing.
