You can still run your 7 bolt tranny with a 6 bolt bottom, just need to swap flywheels. If I built a 6 bottom, wasn't planning on ditching my TRE tranny & would keep the 7 bolt head/evoIII intake mani.

Yes, the revised split thrust was Mitsu's design to prevent CW. Don't think it completely eliminates it but it does seem to help vs previous gen 7 bolts. Again, alot has to do with the builder. If I go 7, I also plan on having the oil squirters welded shut. You don't need them with aftermarket pistons & that can help eliminate a possible cause of CW. Apparently they can fail in the open position (if you've seen a pic their much smaller then 6 bolt squirters), which causes them to continue to squirt when they aren't supposed to, like at low rpms, such as idle. This can take the oil supply away from the crank mains. So from what I've heard its a good idea to eliminate them.