New seats?

most likely will need to be custom made if you want an air ride. Air seats sit on a raised platform so the bladder can fit under neath it, at least on school buses. You need to probably go to a truck sales and see what they have for a medium duty truck. Plus you will need to install a compressor and air tank to keep it inflated. The bus I currently drive has one and it is really NOT comfortable and the thing is either too high or too low and it bounces all the time as a result.

A better option would be custom seats from a racing outfit, or possibly have your truck seats redone at an upholstery shop and have them use a better foam.