It would probably be easier just to find a set of 52-55 doors. The entire latch assembly inside the door is different, the striker on the cab is different, and the mounting holes for the handle are different. It has been a number of years, but in the past I tried to convert a 52 door to the turn down handle for use on my 51. Nothing fit right, and I wound up finding a good 51 door instead.

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