>how about the 7.3 liter? does a ford truck or van classify? i don't know the answer.<
The 7.3 L is a bored out 6.9L ( 0.110 IIRC) This is the reason the 7.3s need the cooling systems properly maintained. Cylinder walls are thinner.
My busses are both 7.3s, same motor basically as the 6.9 in my F250.
Ford trucks and vans use the same motor as the 7.3s in busses, but Ford uses an adapter plate to mate their transmissions to the IH motor. I could if I needed to , put the 6.9 from my F250 in my bus, or vice versa using the adapter plate thats already in my truck. Only differences that I see are bolt on things like the water neck and oil pan and accesories. I run the synthetic in the bus's 7.3 too, it sounds very different and feels like it doesn't work as hard .