Transit bus drivers are subjected to the worst "wear & tear" on the body that occurs to professional drivers. Transit properties who wish to keep their worker's comp claims somewhat reasonable take the time to research and purchase decent operator's seats for their staff.
I've seen National, American, ISRI, Recaro and USSC seating in various models, but never a Bostrom. Dunno why.
Interestingly, the old, original National low-back seats found in 4104s, 4106s and other bus brands from those days are surprisingly comfortable for the long-haul. Provided, of course, that the seat cushions and padding are in good shape. (Much better than an air-ride if you still have a stick shift, too.)
ISRI makes a good seat, but they tend to be maintenance-intensive, and sourcing parts is a challenge.
Recaros, for all their glory in Porsches, are quite lacking in their commercial line. Oh, they've got the bolsters, etc., to support you this way and that, but they tend to have very shallow cushions for your butt to plant itself upon. In transit use, they usually lasted about three years before the cushions had to be sent out to be repaired. Drivers would refuse to take out a Recaro coach after sitting down and feeling the only thing underneath you was the steel frame. These cushions also tended to be short, so taller drivers didn't have a lot of thigh support.
USSC makes some very interesting seats that are conceptually similar to Recaros. The one difference, and it's a BIG difference, is the size and depth of the cushion you sit on. They excel here where Recaro falls short, as the cushions are much thicker, which really helps when you're spending 8 - 10 hrs per day sitting.
The USSC and old National seats produced the fewest back injury claims, too.
I have no experience with Bostroms, since I never spent any time in the trucking industry. I will say, however, that an air-ride seat with a manual gearbox coach is a PITA, much more so than an air throttle/stick-shift combo. OTOH, an air-ride seat in an air-ride bus, altho almost overkill, is a very pleasant experience if you've got an automatic. An air-ride seat in an Eagle would be fantastic - UNLESS the coach's shocks were bad, in which case you'd better have your seatbelt on. Otherwise, you could easily be bucked out of the seat under certain conditions of pavement undulations. (Non-air ride seats, too!)
You might actually be pleasantly surprised at how comfortable an original, hi-back MC-9 National driver's seat would be in your 5C, and at far less cost than a fancy air-ride. Simple bolt-in replacement, too. Something to consider, anyway.
FWIW & HTH. . .