There were two suspension under these cars.
Base on the Fifth Avenue was conventional front struts, rear coils and automatic air adjustable shocks (basically a conventional air shock with a height sensor). It's easy to install regular manually adjustable air shocks.
Upgrade was the full air suspension with a bad at every wheel, front and rear. Not hard to convert, but you need strut assemblies for the front, coils and conventional shocks for the rear.
Base on the Fifth Avenue was conventional front struts, rear coils and automatic air adjustable shocks (basically a conventional air shock with a height sensor). It's easy to install regular manually adjustable air shocks.
Upgrade was the full air suspension with a bad at every wheel, front and rear. Not hard to convert, but you need strut assemblies for the front, coils and conventional shocks for the rear.