Frames and pans are the same.
Boxes that spring perch hangs from is different between Dodge and Plymouth.
Inner wheel houses are the same between Dodge and Plymouth and 4-dr and 2-dr. Outer wheel houses are the same between Plymouth 2-dr and 4-dr but are different than Dodge. Also Dodge outers are different between 2-dr and 4-dr un-like Plymouth.
Also rear cross member is probably different. 68 has a round hole for the fuel tank filler tube and 69 is probably oval.