I just formally added the trailer to the registry, and it sure does look in great shape!! I believe the one whitewall tire might be original- they did often put whitewalls on them new back then! Is it a trailer tire? What brand/model is that one?
I believe your trailer was built earlier than I originally thought, probably late June or July of 1980. Very early in the model year. Around 200 units in to a 1700 unit model year roughly.
My only concern in the pictures- I see it had an awning at one time, and the top brackets were removed. Make sure the holes left from those are sealed up, so that water doesn't get it in.
2007 T-286SR Cherry/Granola, #6236, original owner, current mileage: 9467.8 (as of 5/26/19)
1997 T-2653 Blue Denim, #5471
1979 12 1/2' MC, Beige & Avocado, #4639
Past Sunlines: '97 T-2653 #5089, '94 T-2251, '86 T-1550, '94 T-2363, '98 T-270SR