3rd gen spare?

hello everyone. i work at a tire shop and a 3rd gen 1500 came in today with a flat. he had his spare on which was a 20" steelie. now i have to have 20" steelies but im not sure if the 8 lug trucks got them or just the 5 lug? we do send out wheels to get widened in new jersey and i know stockton wheel (also widens steelies) in cali will put different centers in steelies so maybe if they only come in 1500's i can have the centers from my 16"s swapped in the 20s. thanks for any tips-chuck