The drive axle parts are available from any big box auto parts retailer such as AutoZone, NAPA, etc. under a P30 Chassis for the same year as your motorhome. Fleetpride usually carries the heavy duty stuff (air bags, etc.).
The tags are actually off of an Airstream trailer. You should be able to get these from an Airstream dealer or from Inland, Vintage Trailers, etc.
Have to ask - what happened?
1986 Airstream 345 Classic Motorhome