My truck has the tie down latches for putting it in the center seat. Of course mine is a reg cab and I would not put him in there unless there was no other choice. We have our sins car seat in my wifes nitro behind the passenger seat. It uses the belt and it is tight as tight can be. The latches though is for the side seats not the center seat.
According to the fire department here, number one safest place is in the center seat. If you were ever in an accident that is the safest place. Second safest is behind drivers seat because if you were ever t boned more often than not its going to happen when you turn left which puts the car seat directly in line with the oncoming vehicle. Passenger side is not necessarily the worst but because of the reason stated before there is that chance that it could become the most dangerous. Reason we put it in the passenger side is because it was just more convenient. When driving with the family I dont take any chances when it comes to turning, changing lanes, speed etc.