Infant seats for 1991 t4 trident

Hi- new here! We bought a 1991 t4 trident auto sleeper just over a year ago. We’ve spent some time cleaning it up a bit and hoped to get away in it this spring/summer with our two small boys- 7 months and 2.5years. However I’m now realising it may just not be suitable to carry infant seats and panicking!! 

Does anyone own one and been in a similar position?? Our van has an extra seat added behind the passenger seat which we hoped to use but apparently it’s a no no as it’s rear faces. (We do need to try and see if it fits facing the front but I don’t think there is going to be room). The rock n roll seat belts are 3 points but the clip part in the seat is on a longer tether and the seat we tried to fit told us this was unsuitable. 

Has anyone managed this or got any advice?