Diesel Bombers - wheel spacers, and multiple wheel spacers

so i need some help, i have a suburban and im putting in a 3/4 ton 14 bolt not sure if its ff or sf as i havent bought it yet but will be picking it up in a couple days. m y problem lies with the fact that i want to make it a dually and i dont know if any of you chevy guys can help me ill be running 16.5 dually wheels with 36/12.50 bias ply military tires and of course a two inch wheel spacers in between but will the dually wheels fit or since a pickup dually axle is 4.5 inches wider can i make adapters similar to that of a front dually adapter out of a solid piece of steel sorry if this is kind of all over the place but will it be safe if i make the adapters and run a 2 inch wheel spacer in between