the Genesis, Gen LE and GST all have a 3 speed tranny w/reverse, the Nemesis has a 2 speed no reverse. They didnt put a 3 speed in the Nemesis because it is geared more for track use. They also didnt add the upper horizontal shock and a few other things to save weight.
The Nemesis and GST both use MTM brake system. The Genesis and Gen LE do not.
People talk about part being hard to get but if you go on ebay you can usually get replacement parts and the upgraded GST parts pretty quick and cheap!
You can go to the site below to check out the three CEN trucks we are talking about too
http://www.cenracing.com/rckits.html