There are a number of threads on alternator conversion, so I won't repeat much of the info - fairly easy to do - and brackets are available from the usual suppliers. Here's one vendor by way of example (no affiliation) that makes every type of bracket imaginable for these engines:
Chevy 235/261 Brackets.
Here's a brief summary of
Delco options for commonly used 10Si or 12Si alternators (internally regulated), including their original GM service fitment, which helps if you source a remanufactured alternator from a local parts store. For most fairly stock vehicles, the added cost, higher amperage of further upgrade to CS-130/144 alternators isn't needed.
It pays to find true Delco-Remy alternators in my experience. There are various models that are clocked differently, which facilitates mounting on the passenger side of the engine, if that's desired. Here's another article that explains more on that, and at the very end lists more part numbers and original GM applications.
More on 10Si and 12Si alternator selection.
Although there are pros & con of one-wire vs three-wire alternators, I prefer three-wire, since that style allows running the sense wire closer to the battery for better charging regulation, and there's never an issue with self-exciting the alternator. It's a toss-up, otherwise. Simplified three-wire diagram, inserted for reference.
Hope that helps.
Doug
