Shop your local LKQ yard or local Pull A Part yard.
1990's conversion vans with fiberglass tall and short rooftops come in all the time at these yards and you will never pay more than $200 for the complete roof cut.
I just purchased a complete VW Vanagon Westfalia pop top roof cut last Sunday at my local LKQ yard for $75.00!
For $3500 that USED fiberglass rooftop referenced above should be stripped, painted and INSTALLED on your van by the seller!
For $3500 or less and maybe a lot less you can buy whole vans with complete tall rooftops at Copart and in most cases sell enough parts to git PAID to install your new tall top on your van!
Remember "Drive Fast, Turn Heads, Break Hearts!"
2001 Chevrolet Express 3500 Quigley 4WD ATF "Bomber Van"
1995 Chevrolet ASSTRO 4WD Quigley Custom Van
1994 Dodge B350 Sportsmobile Van