manifold questions

the manifolds im using are 3418623 right and left 3614368..the 623 has a raised flange and the 368 is a flat.surface..both are supposedly off the same car and year..was this how mp shipped the car or did left and right have the same raised or flat surface..supposedly by the book,this car calls for gaskets on both sidesany help or ideas on this..im uing them on a 73 duster ex slant car...thanks..j