1. A 58 is a 12V motor. I assume you have worked that out.
2. I assume you know what you are saying is true, but how do you know the fuel pump is bad?
3. Your only question is: "are 53 and 58 the same pump."
Do you have the dual action vacuum for wipers or single action for electric wipers?
4. Websites list different part numbers for the pumps in 53 and 58. However I believe they are the same physically. They do have have different flows. Single stage: 53 is 20 GPM and 5 psi max. 58 is 25 GPM and 4 psi max. Depending on carb, your choice. I would find out what motor I had if I were you. With tolerances and your hybrid system, they can be called the same pump.
1953 Carter M2118
1958 Carter M2999
In the dual stage pump versions for 53 and 58, the PSI's cross over each other. So more evidence of either pump for either motor.
Thanks for the info. Look at my other reply. I's not the pump
