This should help from ETrailer.com
Sunline did follow the industry standard wiring setup. Your truck should also be following this. If by chance your camper has back up lights, the round pin in the center of the 7 wire is the back up light wire. #7 labeled auxiliary. Some of the older 80's campers did have back up lights. I do not know what exact years but I "think" by the late 80's and into the 90's they where gone. Wish they had them.
Hope this helps
Current Sunlines: 2004 T310SR, 2004 T1950, 2004 T2475, 2007 T2499, 2004 T317SR
Prior Sunlines: 2004 T2499 - Fern Blue
2005 Ford F350 Lariat, 6.8L V10 W/ 4.10 rear axle, CC, Short Bed, SRW. Reese HP trunnion bar hitch W/ HP DC
Google Custom Search For Sunline Owners Club