171L bracket fits driver side of a 1963-1964 Chevrolet Passenger Car. It is used to mount a spotlight with a F length shaft through the fender.
185L bracket is for driver side of 1967 to 1972 Ford F100 - F750 mounts through the cowl useing a spotlight with a P length shaft. It also fits driver side of 1964 regular sized pontaics. P length spotlight through fender.
For 1987 Chevrolet Pickup we cannot provide correct parts without knowing what model it is. Chevrolet had several pick ups tht used different parts that year. C series, K series, R series, S series, V series