Two 87 Buick grand nationals with Consecutive vin number. Rare???

Im trying to find the value of two 1987 Buick grand nationals. My father owned a buick dealership way back then and he kept these two GN's because they had consecutive vin numbers. neither has been tagged or titled. Both cars have less than 1,000 miles and are 100% original they even have the price stickers on the window. Im not sure if consecutive vin numbers increases the value or if I should sell them separate? Thanks for any and all input on this!