First of all, something doesn't add up. Sunline did not built the StarRay model in 1978. If you are pretty certain it is a '78, send me your VIN and a couple pics (if possible) in a PM.
As for tank sizes, go to the brochures section. The StarRay was built from '89-'91, so any of those three brochures should help you. Just match up a floorplan and follow that number to the table of specs. I can't really find the # for you because there are a lot of different 27' models.
Here's a link: http://www.sunlineclub.com/brochures.html
As for your question about the stereo, I responded to it when Kathy posted it: http://www.sunlineclub.com/forums/ph...pic.php?t=1091
Let me know if you have any questions,
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