Still not sure what the "sb" stands for but I think I get what you're saying.

The reason for the Jeep 4.0 is because it's basically the same as the 258 so I can use the same mounts, tranny, etc. The drawbacks so far have been that I have to use a few aftermarket things to get it runnin from a carb to a fuel injected engine. Otherwise, it's fine.
Oh yeah, the other drawback is wiring. There are many things you can do including use a $400+ harness from Hesco but I'm trying to avoid that.

When I'm done, I'll have a pretty well running CJ that's going to last for quite awhile.