You will need a low-rider seat base with a short vertical travel or you will have a dent in your roof and your head everytime you hit a bump. :{
There are low bases available for Class 6-8 trucks, Peterbilt drivers get them from us so they can sit way down for whatever reason. I think they still have too much travel for a pick-up cab.
The seat bases shown on the site early in this post are National Seating, but they are not part numbers that show up in any of my pricing media so probably not available to us Class 8 guys. Using the suspension that the mentioned site sells would give the greatest satisfaction as putting a Class 8 base in a pick-up is gonna' be a project and could be down right dangerous. Not to mention getting the seat belts to be safe again. Please proceed carefully, there is a reason that these are not readily available, it is called LIABILITY.
There is a low mount, short travel base that I have seen in the 5500 series GM trucks that would most likely work as that is roughly the same dimensions as a pick-up cab. Has a lever pump to adjust the height but that may be because they have juice brakes. If you have an air source then maybe it could be valved in. Something to look at, anyhow.
Whatever you decide on, please keep safety in mind. Just imagine a seat breaking loose from it's mounts in a turn at speed, or getting in an accident and having the seat break free. Be SAFE.
One more thought ****Don't forget the air bag**** On a Class 8 with an air suspension seat and an air bag, there is a mechanism that locks the seat in place before the air bag deploys. Just think that through for a minute.