I have a 2003 f7 and i want to update it to 2005 or06 specs.First I'm going to put a new seat on it should I go with the 05 or 06 which is thicker?And is that 4th wheel kit worth it as far as handing better and being more stable?Is there anthing else I should do to update it?

The seat is a great place to start. 05 or 06 are both good not sure of difference in foam though, I can't tell the difference. The speedo sucks but it is functional. At a later date I would have ecu reprogrammed from Cat with 06 updates, makes all the difference for stock performance. Wheels are your choice.