I found 3 of the old stock steel rims today at the pull a part. They were all stamped with 15x6. Do all of these rims have the same back spacing? And shouldn't the stock hub caps fit them?
Thanks
Scott
Well, by "hub caps" I assume you mean the factory full wheel covers that were optional from '67 to '77.
In that event, there will be a difference in how they fit. Not from a diameter standpoint, but by where they sit in relation to the front hubs. With the conical shape of them, the hub and locking knob will sit flush or just beyond the opening on stock 15x5.5 wheels. If the wheels have too much positive offset (like on a 6" or especially 7"' width), the hub and knob will be recessed from the opening. Look through the Gallery here to see images of Broncos with stock wheels and wheel covers and you'll get an idea.
Now, if you're thinking of going with true hub caps, the kind that snap over those raised bumps in the steel wheels just outside the bolt circle, then it really won't matter. They'll fit any kind of steel wheel, regardless of width or diameter.