1970 Chrysler Electrical function and upgrade

I put a bit of work into this boat in the last few month and is well deserved. Everytime we go out I always bring an extra battery and cables just in case.
I have looked into having the existing alternator refurbished but not even sure how it works with the alternator, resistors and regulator. This system actually works in this boat as is and continues to work. I am always in fear of it failing at some point. I like to upgrade it and keep it looking original maybe even leave the old pieces on the engine. I know there are many creative people on this site or at least tell me how this works for piece of mind. Times like this I miss my grandfather who could explain this old technology to me. Currently everything is working as it should. I am ready to install new battery cables and update the electrical to give me piece of mind out on the water. This is my first post so let me know if I did something wrong.

Thank you
Marc

https://photos.app.goo.gl/cZ7RLk5w36a6yxxp6



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runs perfect and charges at 13.5v.   those two resistors Look scary to me being 50yrs old now. Same as me. Ha, I just look at them and think i can make it better.

So your saying bring my spare battery and be happy.

Manual is awesome. Thanks, Thinking the old technology may be the most reliable!!

There is one on top by the coil and the other big box looks to be a voltage regulator from the manual. I am planning to look up the numbers tomorrow and maybe just replace them.