Differences in crate engines?

[freak]

I see at Jegs a lot of 4.0 OHV's with codes such as DFK5, DFK6, DFT5, DFT4, DFZ8. What is the difference in all of these. It lists different years but was something changed so that one won't work in place of another?

 

[410Fortune]

I often put 98-2000 ohv blocks into older trucks
I would get the latest version you can the heads were updated several times over the years the 96+ are stronger

Now for crate engine I doubt there are many changes inside the long block
The changes were all
To intakes and accessories