I've only got info that goes back to '74, and that's for the 454. There's not that big a difference as for labor, though. RTLG lists it as 13.1 to 14.7 hours without A/C and with P/S. 13.6 to 15.2 with A/C and P/S. However, on custom work, I have a whole diffe... Login to read more.