mikebreeze wrote:
I have an E350 chassis and had my shocks replaced a few years ago because one of mine was leaking.  I went with some heavy duty Monroe Shocks.  I had an independent shop install mine.
  A lot of people go with Bilstein or Koni shocks.  
I had some major steering control issues at highway speeds initially.  However, after replacing the front shocks, ball joints, front tires and getting a front wheel alignment, my rig now is very stable at highway speeds.
X2
I have a E450 and went with the Monroe shocks also. 
I watched the frame shop install them - REAL glad I didn't attempt to do it! :W
Made a big difference in handling. 
RV friends who went that way of Billstein or Koni said it made for an unnecessary hard ride.