In 1972 the UAW strike lasted 174 days, stopping production at the Ohio plant. The result was 1100 Camaro's failing to meet 1973 Federal bumper safety standards. http://www.conceptcarz.com/vehicle/z169/Chevrolet-Camaro-RS.aspx
GM went on strike due to the Vietnam War. Some cars were finished with Buick interiors to go around. http://www.chevellesrus.com/parts/1968.html
Chevelles had Buick interiors possibly due to race riots in Baltimore & KC in early April associated with MLK assasination, and not a strike http://www.chevelles.com/forums/showthread.php?t=229304
Rather than stop production, assembly plants in Baltimore, Fremont, and Kansas City went to Buick and Oldsmobile for door panels and seat covers. A large number of '68 Chevelles from March to june of '68 had Buick and Olds interiors. Muscle Car Review, March 2009 issue, page 36
April 1oth was the start of a strike that lasted until June 9th. This stopped production of Corvettes, forcing Delorean to continue the production of 1969 Corvettes past the ordinary Sept time of a new model year... causing a all time high production of Corvettes of 38762 units. This also was a cause of low quality control in the 1969 model Corvette. A 1970 Road and Track survey had quality as the worst feature of the Corvette
The April 6 1970 to May 6 strike of the Teamsters and the late start of the '70 vette caused a low production number of just 17316