Most of the Civic and CRX are exactly the same. However its mainly like...

Civic STD/CRX HF
Civic DX/CRX DX
Civic Si/CRX Si

There are some differences such as STD had a B1 and HF had a B6 which was MPFI. But they have the same knuckles and stuff. The DX and Sis are more like each other though.