Child seats in 65 66 fastback

[vibe65]

As title suggest im after advice or recomedations on child booster seats forward facing that fits in the fastback rear seats. I have harness and lap belts fitted in back but as the seats are 2+2 and not a bench as in coupe the seat doesnt sit in very well from our other car. Plus the seat back is lower then modern cars so if anyone is using child booster seats in early fastback can you pass on some info or pics. Thanks