[bouncytruck]

I did extensive research on child seats in the Blazer.

I used child seats for both my kids without any issue. Child seats are generally higher than the child's head which should add some protection in the event of a roll over. If you are concerned about a roll over, I would add a family cage to your truck.

I do not use booster seats. Booster seats are designed to position the child for the shoulder belt. With lap belt only seats, it is safer for the child to sit directly on the seat than use a booster. I confirmed this with the Washington State DOT and the WA State Patrol.

They do make safety seats that have 5pt harness for children up to the age of 8. All of them require modifications to vehicles belts and/or add mounting points.