Hey Rich -
First I want to ensure you’re aware of the search function on the JL site. It will come in handy for sure. If you’re not familiar with it notice the magnifying glass up in the top right corner. If you need help figuring it out, just say so! Half of the challenge is figuring out the right terms to search for!
Here’s a link to a post I found that shows a picture of the relays on the LHS splash shield, and their proper order. Maybe it’ll be helpful for you:
As far as alternators, the 10SI is widely used so I suspect you should be able to find one. I had one in my '68 but it was toast, and I ended up using a 12SI for the better cooling design. I wrote a little about it here, and some of my experience with aftermarket relays and wiring: