I got DS a new carseat for Christmas, he was 4 months old and he was only 3 pounds lighter but taller than your son. I got him the Graco My Size 70. We were driving a chevy aveo LS and it fit in it, not as comfortably as we wud like but better than his infant seat. We now have a 2007 Chevy Equinox and it fits GREAT! It has a 8 point adjustable headrest and rear faces untill 40 pounds and has a recline. It forward faces from 20-70 pounds.