Replacement manifolds for 360 in a 74 Duster?

mopar 4me where is the passenger side, u show 2 drivers. chinese crappy castings. old castings are easily checked for cracks

Agreed, in-hand original casting can be checked easily, I have added the passenger side, the pics I included are directly off of the venders ebay link.

They are not mine, though I do have a few original HP sets both early and latter design if OP redecides to explore that rout.