Welcome, you have the big six---either a 251 or 265. The 265 was used in the 52-54 Chrysler`s--251`s were used in the Desoto`s. As these engines were interchangable you may have one or the other. Look on the drivers side of the block near the front there is an area that is flat just below the head--this has the ID numbers stamped there. What is wrong with exhaust manifold--cracked or rust hole?? Maybe you just need a new gasket. I do have an extra manifold that I may part with. Good Luck......52er
