Your 1957 RD-19 is one of the easiest ones there are to convert. It came from the factory ready to convert with a fuel pump conversion kit. Here is a picture showing the original kit installed.
For clarity, I’ll be using some newer models to illustrate how it’s done. Your 1957 will already have the proper bypass cover to mount the pump on. Just drill the center hole on thru and tap #10-24 threads in the other two holes.
Pump shown is one of the best ever made but is obsolete or hard to find or expensive. Fortunately, there are many replacements/substitutes out there. Of course you will have to reroute the hoses through the jungle of parts on your 35
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Finally, remove the air hose from intake manifold and block or plug the fitting.