They are basically the same, at least in appearance, obvious main difference being the front end area.

1968 Chevy Camaro

1968 Pontiac Firebird
Yup. The sheet metal is even closer than Mopar brand sibling cars. However, unlike Mopars, GM brands had their own engines, so the Camaro and Firebird were not mechanically the same. Different bolt patern on the the transmission bell housing too. Also, the Firebird’s suspension was lower.