Well I priced 50 in cloth at 37.50 a yard.  weight was 5.7 oz per ft
sq.  Basic Van  is 15 x 6 feet, or 90 ft sq so this give us 10 yards
approx or $375 for the cloth.  The wet out could be done at .75 oz per
ft sq or 90 oz so a gallon of resin. at $100 or $150 for epoxy resin

The basic questions on  how to approach this is : Cosmetic or
Replacement.  If your after a cosmetic carbon fiber look the above
approach would be in my opinion the best.  Use surfboard polyester
resin, it's clear.  If you go the west system type epoxy, then you'll
need to clear coat with a uv protection.  At this level I'm not going
into "how to" just a slightly more than armchair Quarterback approach.
BTW, since stress loads are carried by the skin and not the interior of
the panel, the cosmetic approach get you a good deal more strength in
the tension on the top, not sure how you'd benefit from this.

To make a top, you don't need to make a mold from scratch, as long as
it's just for you, you could do this.  Take an existing top, and brace
it  so that it is stiff, and then do the wax and release prep, omitting
details, then do a 4 layer unit of :1oz mat, followed with 18 0z woven
roven.  This is your mold, factory setup would allow this to cure in
place for 2-3 woks, then remove and stiffen it  all squared up. Now your
ready to do your layup prep, wax etc.  Then the carbon fiber ,  foam
core it and glass the inside .

In my opinion  the top would be significantly lighter, and thus a more
stable van.  Too, if you can do this or pay for this, the options to
modify to suit are there.  As to a very general rule of thumb 4x the
cost of the cosmetic would get you the glass, and the foam core by ACT
is $150 sheet, best price I can think of, which is 1/2" x 48" x 96" so
probably 4 sheets or  $600.  So no labor cost, I'm seeing $1800 as a
minimum. Oh one other benefit is the the insulating value of a cored piece.

The downside to me is that carbon fiber being black would be a hotter
piece; and a possibility of  some post curing deformation, What exactly
I don't know, but possibly some visible buckle or perhaps a warp where a
gasket surface meet. Somebody would be the guinea pig.

Hope that puts more stew in the pot.  Any questions p-mail  too, since
I'm on digest.

Mark Keller