RE: Tuning nightmare
Just my 2 cents. The problem with the tuning on the 3.3 and 2.5 is the cooling head. Get an ACNCM cooling head or nova racing and replace the stock. It will do wonders!
Also on the 3.3 the con rod can be upgraded before break in to the Davis Diesel one and it seems to work pretty well. I don't expect my engine to blow prematurely due to the con rod.
3.3 is great if you change cooling head.
Just a note: If you put a 3.3 in a 2.5 it will twist the heck out of the drive shafts. Diffs will hold up because they are the same material and design. The other thing that will suffer is twist in the chasis since the 2.5 plate is a bit thinner I think. I did that years ago on one of my Tmaxxes and the chasis kept flexing and stripping my spurgear