DESIGN CHANGE EFFECTIVE POINT 1975 GMC MODELS 1975 First Design Prior to Serial No 582529 With Out MVSS121l Serial N0 582529 thru 589999 are Void 1975 Second Design Effective with Serial No 590000 With MVSS121 1975 CHEVROLET MODELS 1975 First Design Prior tc Serial No 134487 With Out MVSS121l Serial No 134487 thru 139999 are Void 1975 Second Design Effective with Serial No 140000 With MVSS121l 1976 GMC MODELS 1976 First Design Effective with Serial N0 555001 thru 564724 1976 Second Design Effective with Serial No 570000 NOTE The Following Serial No that fall in 1976 First Design are Effective with 1976 Second Design 556934 561396 561829 564297 564302 556948 561825 561830 564298 564303 556952 561826 561832 564299 556954 561827 561833 564300 556958 561828 564296 564301 1976 CHEVROLET MODELS 1976 First Design Effective with Serial N0 100001 thru 118079 1976 Second Design Effective with Serial No 120000 8