I feel your pain. I have low back issues too and when it gets bad, I have sciatic pain going down my right leg. Mine stems from an injury at work, and then all the miles of running and biking don't help. For the truck, you need to find something with good lumbar support. Most seats, even ones with lumbar control still don't have enough. You are trying to keep your back in the natural curve so that your vertebrae are not squeazing your disc that is giving you trouble.
Ice, when you are laying down helps me, as does stretching and IB in the morning.
On my Tacoma, I put in leather heated seats and they have worked wonders. My 84 still has the stock SR5 seats, and I think I am going to have them reupholstered with more lumber and side support.
One more thing, its not just the lumbar, but also the angle that the seat puts you in, so be careful when you transplant seats to get the right "seated" position.
