On the old trucks there wasn't a spacer from the factory, the hub flange was all 1 piece. The aftermarket makes some that bolt to a single wheel hub. I have some factory dually hubs if that would work for you.
The axle I bought had some on it it's a Dana 60 kingpin I was told it was a late 80s early 90s Axle I just have to have some spacers so I can put my wheels and tires on my truck and they are hitting the leaf springs. But what I'm looking for slides over the 4x4 hub and is a little over 4 inches long or so