A.T.
Absolutely any seat will fit rear facing in the back of a silverado. By 7 months your child should have enough head control to where they don't need to be as reclined as when they they were newborns. I absolutely do not recommend a comfortsport, they are the earliest outgrown of almost all convertible seats because of their low shell and harness slots and they only go to 30lbs rear facing. When you go carseat shopping take a small measuring tape with you, I use a sewing one. What you want to measure is the seat part of the carseat to the top harness slot and the higher the number the better. No matter what the weight limit is on a seat all forward facing seats are outgrown when the child's shoulders go above the highest slots. Once you measure a couple of seats you'll see what a difference there is. I personally love britax, but the new evenflo advance is nice as is the safety 1st uptown and fisher price safe voyage.