Mike,
I converted my '54 a long time ago. The stock setup, i.e. push button starters and generators, was still in use when jeeps were converted over to 12V during production. This is what I did; I got a 12V generator/regulator and left the 6V starter in place. No bracket or fitment issues. No additional grinding to get aftermarket parts to fit. I am however, looking at some kind of maintenance down the road on that 6V starter. My biggest bonus is it "looks" stock.
You don't need a new starter but you do have to understand that the 6V starter will turn faster. It will engage the ring gear harder and will have a shorter overall life span. It can however be rebuilt. It can also be replaced with a stock 12V (some have posted the 6V can be rewired - beyond my garage skill set). Whether to use the push button or not is up to you. The 3-way ignition switch has no momentary on, like a modern ignition, so there needs to be a spring loaded starter function, a.k.a. foot switch. There are ways to convert to using a solenoid if you prefer.
Reading the article on alternators on the CJ3B Page or scanning all the posts about converting will let you know that other alternators will work and which is preferable (sometimes based on availability). You will need a different bracket to allow a decent sweep for the alternator so you can remove and install/tension the belt as well as aligning it with the other pulleys. The vendor offered conversion kit is intended to be a "one stop shop" conversion but you will still need to alter your harness just a bit to compensate. Pricing salvage parts and then sourcing a bracket will tell you whether you'll save overall (also what's the remaining life-span on that used alternator before it needs new parts?). Typically you match the alternator and regulator to ensure they work together (Note: some of these conversions describe using an alternator with an internal regulator which simplifies installation). I've never tried to mix but I'm sure others have and can describe the pros and cons.
The biggest difference between an alternator and a generator isn't voltage. It is possible to find 6V or 12V versions of each. I think the biggest difference is alternators put out more charge at idle. Generators need a little rpm increase to register a charge.
One added bonus now. Since we are sharing bandwidth and combining DJ's and 3B's with the 3A crowd, you are effectively doubling the available expertise and knowledge base that could offer advice. So get ready for a lot of input.
