I always felt it was an HO because of the exhaust manifolds. At the time it was the only car I ever saw that came with them. This thread has some good info about the traction bars. Traction bars thread It seems that the manual trans cars needed them the most. A friend had a 1967 400 but with automatic- no bars at all. Something about that high compression 1967 400 I had: when I took it apart- all the piston ring lands were broken. I would guess that when the lead was removed from the gas the 400 must have pinged like crazy. Being an NYPD car they probably just drove it to death and didn't care.