1966 West Coaster USPS Mail Carrier

While I lived in Florida I came across this scooter back in a lawnmower shop fenced area. I asked about it and came to trade a two man fiberglass boat and trailer for the scooter. Price came to $250.00 .
After finding what I had , I started to rebuild it , it has a 3 speed Borg Warner Trans w/ rev, an original Onan 2 cylinder with the extra fan blade on the engine . The scooter has bike streering and Ford Cortina brakes, all original items ...
It would be nice to know what this item could bring either at auction or what a collector would invest for it ?
I contacted Onan about the engine and they said they'd get back to me, well the next day I heard from Onan and discovered this engine was registered to the US Postal Service in Tampa,and there was only 338 made for inner city mail delivery.
The Postal General in Washington DC also has one, but asked where I got to find parts, I have my sources...
Can anyone inform me of any extra info I can use for the scooter ?

Enjoy ,

Richard Soles
Warne,NC