They should be side specific, accounting for the taper of the frame from front to rear. At least they are on a 3100.

Yep, FAM indicates left and right for all models for the front brackets, a single PN for center brackets, and left and right for MOST 3600 models for rear brackets.

Kevin
1951 Chevy 3100 work truck
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1929 Ford pickup restored from the ground up. | 1929 Ford Special Coupe (First car)
Busting rust since the mid-60's
If you're smart enough to take it apart, you darn well better be smart enough to put it back together.