So far we are impressed with the new Peninsular 6.5 diesel in the old truck. About 27 mpg (imperial) and very good power. Maybe we need a couple more tires under it though?
Do as I did to my 96. Put an upper 6 leaf instead of the 5 pack, with all the leafs being 1/16" thicker. Gave me an 8500 lb pack instead of STD 6400 rated spring pack.
I've also heard good things about the penninsular diesel for 12+ years now. If I still had the 96 and that motor went out, I would get one from them.