I would replace both air bags. Good chance the other one is just as old and rubber, just like your tires, don't last forever!
If your system is a Super Ride (American Carrier Equipment, or American Carrier Systems, same company) These should be the bags you need. This was removed from a DIY for my 310 I did for another site.
You can purchase all that is needed from ACE, manuals and parts, but I purchased the Firestone bags from Truck Parts and Accessories for Pickup Trucks, Medium Duty Trucks, Semis, and RVs - TruckSpring.com
The Firestone air bag number from Truckspring.com: W01-358-5412
ACE Part number: 8003-011
One of the problems I have seen in other forums is that some people have listed the wrong air bags for people to get. The bags needed for our rigs have an internal stop to keep you up if for some reason you loose air. Also while setting, the system as it looses air will rest on these internal stops.
If you want the article, I can email it or PM you it.
Chris & Brenda, Members of the Christian Motorcyclists Association
AIR Member 12654
1982 310 MoHo
Many Years ago, 1972 Argosy 24' trailer
Our Toad, 96 Saturn SW2 (250,000 and still going