This is an original NOS unit used on all GM models middle to late 70s's.
Fits either LH or RH depending on application.
Check your application as i have also seen applications on Buicks, Pontiacs Oldsmobile's and Chevrolets back to early sixties.
Not a Chinese made unit that you current see on eBay or if you purchase a replacement from parts stores.
Part number superseded earlier part numbers: 5045587, 5045589, 490387, 4906089
Part Number: 4999678