question on these exhaust manifolds

guessing does no good my friend. start with these 2 sites to find your answers.

I'm not real familiar with 68 and earlier cars or big blocks, I have much more to learn. check the drivers side head in the front of the motor just below the valve cover. manufacturing information may be stamped there. that is where it is on a small block. also find the casting number by removing the valve cover, its cast into the outside of one of the exhaust runners I believe or maybe an intake runner.

MyMopar - Mopar Forums & Information - Parts & Accessories Books this is mopar parts catalog.

Mopar Tech Pages this site has a lot of tech on it.