According to the MPC's (Ford and Mercury) the part number is C7ZZ-6503150-A and the call out is for four of them to be installed 1967-68 Mustang and Cougar. They obviously fit into the cut outs on the lower windshield moulding. I found them on 1967 Dearborn and 1968 San Jose Cougars. Never found one in the end position, only the location in the picture which roughly is over the fender and cowl joint. They are visible when installed, barely.
There are 3 different spacers listed for 1969/70.
C9ZZ-6503150-A (MPC) or C9ZB-6503150-F (Body Assy Manual) 1 installed center of cowl, and it is 2 inches wide.
C9ZZ-6503150-B (MPC) or C9ZB-6503150-H (Body Assy Manual) 2 installed per car, one over each fender, and it is 3/4 inches wide.
C9ZZ-6503150-C (MPC) or C9ZB-6503150-G (Body Assy Manual) 4 installed per car, over the cowl and it is 3/4 inches wide.
This shows the differences of them. The 2 inch wide version is the same as the cowl one but 2 inches wide.