I recently picked up a well maintained 300TDT wagon . Bad driver seat and uncomfortable middle seats. I fixed the driver seat by cutting out replacement springs from a junkyard seat and splicing them with heavy cable ties to the broken spring. I also added a 1" thick HD foam between the leaf springs. Worked good.....so far. A bigger problem are the middle seats. They are way squishy and the springs are shot. This wagon must have carried passengers with a BMI way over 30! The springs are a tangled mess of thin linked coils I did add a layer of 1" foam inside after I removed the cover but I would like a better fix. Your back would be toast on a long car trip in the middle seats.