I don't believe it will cover cars in the garage but it should cover garage contents. It could be a fine line determining if pieces of a car are contents.
Are dismantling the truck entirely or could you do a section at a time and still drive it?
Another point is try to get photographs of the truck intact and all the receipts for money you have spent on it. When you start taking it apart again take photos. This will serve twofold, one you will know where the parts go and secondly they may be of use in the case of a loss.
