I wonder if the guy didn't give you the wrong strikers. They should be a direct bolt on replacement. My '51 had a '52 push-button door for years. The strikers mounted in the same place with no fuss. You may need to see about getting a set of used or repro strikers...

-Tim
'51 Chevy 3104 w/'56 235, 848 Head, HEI Dizzy, Corvette Cam, Split Manifold and Dual Carter YF's