Difference in power steering pumps?

Both of my 67 B'cudas had Saginaw pumps. One a 225, other a 273. Oval neck, small cap with 2 little finger bumps on it. That OEM cap is a tough find. So maybe Dodge didn't use Saginaw but Plymouth did.
I bought another Saginaw pump from ebay seller that was yellow paint marked 67 383. Its brackets and pulley are identical to the 273. Maybe it was marked wrong?