Get the propshaft support bearings checked, especially the one in front of the V.C.U. It sometimes shows signs if you have been thru muddy flood water.
Just the normal drive train probs on all freebies but very few with L-Series engine, unless you count the glow plugs when they fail, you can't change No 4 without taking F.I.P off to get at it, other than that and hoses mine has been "good as gold."