I think ome's would be great for a toy on 31's, thats what id do. they will flex better than stock and theyre a quality spring. For the rear I would plan on moving the shackle hanger forward a bit or try the longer 51'' ome rear springs for the 90's pickups.
As i see it thats your best bet. Allpro,tg springs are gonna make your truck look ridiculous on 31's. As for shocks bolt up the springs flex em out an measure, that is the best way to know what size shocks and where to place the mounts.