Well, you have three now, one for low beam, one for high and one for parking lights. So, if you want to be able to join cables for the turn signals, you will need two more terminals. Adding the one with three would give you a spare terminal.

1951 GMC 1 Ton Flatbed -- It is finally on the road and what a great time I have driving it!
1951 1 Ton Completed

My Chevy Master 4 Door is on the Road!