ive seen a number of = burned vanagons.  not all from engine fires either.  but i can tell = you that, yes, the plastic engine lid does burn/melt/cave in on top of the = engine letting flames engulf the interior.  fiberglass burns too. seen many= vans with fiberglass bumpers that were melted.   the safest thing is= changing your fuel lines.  the metal engine lids are heavier, but in= case of a disaster, they will buy you a little more time than a plastic lid, keeping the fire from entering the interior as fast as a plastic lid = would.  the metal lid i have on my waterboxer van is from a 81 westy.  = ;i ripped out that nasty mouse fuzz insulation they had underneath it and installed some of that racing style insulation - looks shiny like = aluminum..it the kind that racecar drivers insulate their firewalls with for noise/= heat insulation. i used the original wire springclips to hold it in place = under the lid. plus i have the sofabed cushion and insulating pad on top of that.   so the noise is not bad at all.

just a fyi.
chris