You probably won't get a valuation on a conversion van from Kelly or NADA books online or at a library. You might want to purchase one of their guides on RV's and motor homes. You will have to get a custom appraisal, which could run $100.00 bucks or more. Look under appraisers and or adjusters in the phone directory and also ask some local insurance agents who does appraisals that are acceptable for insurance.
It may be easier and cheaper to insure the van as a conventional van and just be "self insured" for the conversion items.
And why would you want collision or comprehensive insurance on a 1995 van? They won't give you much for it if it gets totaled. Just go with the liability insurance, IMO.