You can see one possibility HERE
. If you Google P30 airbag you will see a bunch of info.
Regarding the pressure the airbags should be set at :
I had a 96 motor home on a 95 P30/32 chassis. The vehicle owners manual described how to set the pressure in the airbags. In case you don't have the manual this is what mine said:
The owner’s manual gives the following ranges:
4,300 LB front suspensions = 10 psi to 50 psi
5,000 LB front suspensions = 40 psi to 50 psi
5,300 LB front suspensions = 50 psi to 80 psi
5,500 LB front suspensions = 60 psi to 100 psi
For the proper adjustment it says to inflate the air bags to the maximum pressure for your vehicle, load the motor home, park on a level surface and then reduce the air pressure as needed to level the motor home but don’t reduce it below the minimum.
I have seen other schemes for adjusting the pressure per ride quality, but the 1995 Chevrolet Forward Control Chassis owner’s manual said to do it as shown above.
I don't know if it's accurate or not but other posts have said the pressure in the bags affects the alignment and you should have it checked when you get the pressure set. The manual did not mention that however.