I have a fiat scudo van, which was already fibre glassed thoughout in the back. The previous owner used it as a dog warden or something along those lines. There is a divide between the seats and the rear. Now it doesnt seem to be as solid as i would like, just a couple of mm as i was able to drill into it for something i was doing. But my water tank sits neatly upto it and is secured in the van. If i ever have a nasty accident would this supposed bulk head save my life, i doubt it. But then my tank is secured down and not moving nor would travel to pick momentum up to smash through bulk head.
So in essence, does it matter if its there or not, not really or atleast thats how i feel.
It does divide the van nicely though to cabin n rear, so the heating doeant take long to warm the cabby bit for me ☺