You need to look at the backside of the current alternator to see if it's a one wire or multiple wires. A one wire alternator has the voltage regulation built into it, whereas a multiple one uses an external voltage regulator. Far as buying from NAPA, you'll do much better at a discount auto parts store and buy a rebuilt one not a new one. Nothing really to go bad inside one except the slip ring brushes which last a very long time and the diode bridge which also lasts a long time.
I would consult your owners manual to ascertain the output of your present one and then buy a comparable one with the correct drive pulley and if necessary fab the brackets to fit.
Just did that with my 02 Kubota M9 open station. Had a 60 amp one wire on it and the front bearing got noisy so I replaced it with a 100 amp unit with again, internal regulation and I paid less than 65 bucks for it from my buddy who owns a rebuilding business. I wanted the additional amperage because I added some night time illumination to it. They will want your old one in exchange however so expect to pay a refundable core charge which you get back when you turn in the old one. In my case, no core charge because it's a friend of mine but he will get my old shot one anyway at some point.
Same deal applies to brake calipers on your vehicle. I have a buddy that rebuilds brake calipers for a living. He gets bins full of old, leaking nasty calipers and then puts them in a big oven and melts all the components out of them (which he sells to the local scrap yard) and then he bead blasts them and replaced all the melted out components with new stuff and sells them back to the auto parts retailers.
He makes a big buck doing that and has a couple full time employees as well. Recycled and refurbished calipers are just as good as new ones and the same applies to alternators. He does them as well.
His company name is SPB rebuilders btw. Heck of a racket. I get my calipers direct from him and did so with the new rebuilt alternator as well.
Nothing to wear out in one except the diode bridge and possibly the bearings (in my case) and the internal regulator if it has one.