I have recently completed the installation of two child-seats in my 1954 Suburban.
Graco Tranzitions 3 in 1 Harness Booster Seat - @$100 deliveredI used easy to obtain seat belts in the second/third row seats.
These seat belts are used to hold the Booster seats on top of the bench seats.
This arrangement is not only "legal"; it also passed the mother and grandmother test.
If anyone is interested, I will post photos of how I attached the seat belts to bottom-rear of the 2nd 3rd row seat frames.
You could use this "technique" to safely/legally add up to 5 child seats in a 47-55st Suburban. If you have a column shifter, you could add one child seat in the front row of a Suburban; but, I do not think this would be "legal"?
Also, I also use a very wide angle (non-distorting) clip-on in my Suburban.
mirrorIt allows me to see ALL rear passengers AND it allows me to see cars driving/passing on either side of the Suburban.