There will be a label on the drivers door, rear edge, it will have an AXLE code, like "R6"
Look here for what code number means: Ford 7.5 & 8.8 Inch Axle Tag & Door Codes
R6 = Limited Slip(L/S) 8.8", 3.73
Open means one wheel spins
L/S is what Ford calls semi-locking axles, Chevy calls it Posi-traction, both wheels spins
Front axles are pretty much all Open style, only the rear will be L/S.