Based on his Webshot pictures I'd advise him to research all the available 55-59 trucks on the market and find one as well detailed as his own, see what the price is (what you could replace yours for) and insure it for that amount. The rate will probably be a bit rich for most of our pocket books. Your other option is to insure it for coverage for a crash that would not total but would require replacing fenders and doors. Seeing as you are the parent of this vehicle you could save some repair cost by the Ins company replacing parts and you hanging them on.
My two-cents.
