I have a 99 Expy - I hear lots of people talk about the air suspension failing as these trucks get older - Has anyone done an air suspension swap for an F 150 suspension set up?

 

You can't really put an F150's leaf-spring rear suspension in there...I suppose anything is possible, but you can instead just convert it to coils.

This company makes a converstion kit for both front and rear, and others do as well:
http://www.strutmasters.com/catalog.php?cat=52

My 97 rear LLS is still going strong at 133K miles. Never had a problem.When something does go wrong, I'll fix it because I like the advantages of having LLS when towing heavy loads.

I know the search function is not working, but I recall a few people here have done the conversion and have been happy with the results.