one thing i found from multiple insurance companies in my area:
if you have a non-standard body on your truck, the insurance companies may want to consider the truck a commercial vehicle and require a commercial insurance policy. the cost of the policy wasn't drastically different from a passenger vehicle policy, but one nuisance about it is that i have to have separate coverage for each trailer i tow. this can be a pain if you need to haul someone else's trailer on short notice.
i know that there are thousands of trucks on the road that have had the stock bodies rust out and get replaced by various homemade ones, and i'm sure that 99.99% of them never even thought to ask their insurance agent about it. it was brought to my attention by a friend in the business, and i even went to a totally different company and was told the same thing. they even read it to me form a book.
if you do consider this it might be worth asking to see whether your company cares.