92.5-99 (they changed motor half year) have the 7-bolt motor which although is a great motor, is prone to CW unfortunately, not that bad though IMO. Before that were the 6-bolts. The 4-bolt refers to what rear end it has. The 4-bolt rear end is stronger and will hold more power before breaking than the 3-bolt.
EDIT: I knew there was a thread about the differences between 1g motors and rear ends. I found it.
http://www.dsmtalk.com/forums/showth...ghlight=4-bolt
Read through that, it will help you decide which to get.