The reason I posted the picture of the tire on my D100 is because they are P245/75R16s all around and while it almost looks like a 4x4 it is really only 2wd. The real issue here is the gearing...with the 3.21 gears and the tall tires at cruise it pulls the engine way down in the power band. The truck loafs at highway speed and I want to be able to pull a tilt bed trailer with the Ramcharger aboard (about 7,000# altogether). That is why I did the 4 barrel swap and built the Dana 60-2. I want it to think it is a big block 3/4 ton truck. And if that is not the answer, I have a LA318 core and a LA360 core that I can build into 390" or 408" with the 4" cranks that are available. I am lucky in that I have only one axle to change

It almost makes me wish I still had the Cummins