There is a flat to horse shoe adapter for this. My '67 had the flat conn with the adapter and I have seen some with horseshoe only. Not sure when they changed them.
Here are some pics.
Pic 1: left one (From a 1972 C10) has harness with the horseshoe connector only, right one is a new one from a kit that has the flat.
Pic 2: shows the flat to horseshoe adapter.
Pic 3: This is a turnsignal kit from brothers trucks,. If you are going to replace the turnsignal cam kit it they have the horseshoe connecter included.
http://www.brotherstrucks.com/prodin...number=SWTS072
If your turn signal cam and everything else works fine I can send you the flat to horse shoe connector on the left in pic 2 for free million dollars
